tag:blogger.com,1999:blog-3026477688294505402024-03-13T16:02:10.780-07:00HTML 5, CSS 3, Java Script Interview QuestionsAnonymoushttp://www.blogger.com/profile/12478702312334029028noreply@blogger.comBlogger1125tag:blogger.com,1999:blog-302647768829450540.post-56146590127034546972015-05-07T02:16:00.000-07:002015-05-07T02:57:09.491-07:00Introducing Web Workers API<h1 style="background-color: transparent; border: 0px; color: #3d3d3d; font-family: 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 24px; margin: 0px; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; color: #003366; font-family: inherit; font-size: 24pt; font-style: inherit; font-weight: inherit; line-height: 1.5em; margin: 0px; padding: 0px; vertical-align: baseline;">T</span><span style="border: 0px; color: #003366; font-family: inherit; font-size: 24pt; font-style: inherit; font-weight: inherit; line-height: 1.5em; margin: 0px; padding: 0px; vertical-align: baseline;">he Basics of Web Workers</span></h1>
<div>
<span style="border: 0px; color: #003366; font-family: inherit; font-size: 24pt; font-style: inherit; font-weight: inherit; line-height: 1.5em; margin: 0px; padding: 0px; vertical-align: baseline;"></span><br />
<h2 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 24px; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; color: #003366; font-family: inherit; font-size: 24pt; font-style: inherit; font-weight: inherit; line-height: 1.5em; margin: 0px; padding: 0px; vertical-align: baseline;">
The Problem: JavaScript Concurrency</span></h2>
<span style="border: 0px; color: #003366; font-family: inherit; font-size: 24pt; font-style: inherit; font-weight: inherit; line-height: 1.5em; margin: 0px; padding: 0px; vertical-align: baseline;">
</span>
<br />
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
<span style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; color: #003366; font-family: inherit; font-size: large; font-style: inherit; font-weight: inherit; line-height: 1.5em; margin: 0px; padding: 0px; vertical-align: baseline;">There are a number of bottlenecks preventing interesting applications from being ported (say, from server-heavy implementations) to client-side JavaScript. Some of these include browser compatibility, static typing, accessibility, and performance. Fortunately, the latter is quickly becoming a thing of the past as browser vendors rapidly improve the speed of their JavaScript engines.</span></div>
<span style="font-size: large;"><span style="border: 0px; color: #003366; font-family: inherit; font-style: inherit; font-weight: inherit; line-height: 1.5em; margin: 0px; padding: 0px; vertical-align: baseline;">
</span>
</span><br />
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; color: #003366; font-family: inherit; font-size: large; font-style: inherit; font-weight: inherit; line-height: 1.5em; margin: 0px; padding: 0px; vertical-align: baseline;">One thing that's remained a hindrance for JavaScript is actually the language itself. JavaScript is a single-threaded environment, meaning multiple scripts cannot run at the same time. As an example, imagine a site that needs to handle UI events, query and process large amounts of API data, and manipulate the DOM. Pretty common, right? Unfortunately all of that can't be simultaneous due to limitations in browsers' JavaScript runtime. Script execution happens within a single thread.</span></div>
<span style="border: 0px; color: #003366; font-family: inherit; font-size: large; font-style: inherit; font-weight: inherit; line-height: 1.5em; margin: 0px; padding: 0px; vertical-align: baseline;">
</span>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
<span style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; color: #003366; font-family: inherit; font-size: large; font-style: inherit; font-weight: inherit; line-height: 1.5em; margin: 0px; padding: 0px; vertical-align: baseline;">Developers mimic 'concurrency' by using techniques like <code style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">setTimeout()</code>,<code style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">setInterval()</code>, <code style="border-image-outset: initial; border-image-repeat: initial; border-image-slice: initial; border-image-source: initial; border-image-width: initial; border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">XMLHttpRequest</code>, and event handlers. Yes, all of these features run asynchronously, but non-blocking doesn't necessarily mean concurrency. Asynchronous events are processed after the current executing script has yielded. The good news is that HTML5 gives us something better than these hacks!</span></div>
<span style="border: 0px; color: #003366; font-family: inherit; font-size: 24pt; font-style: inherit; font-weight: inherit; line-height: 1.5em; margin: 0px; padding: 0px; vertical-align: baseline;">
<h2 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 24px; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
Introducing Web Workers: Bring Threading to JavaScript</h2>
<div>
<span style="background-color: transparent; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; line-height: 27px;">The </span><a class="jive-link-external-small" href="http://www.whatwg.org/specs/web-workers/current-work/" rel="nofollow" style="background-color: transparent; border: 0px; color: #5073ad; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; line-height: 27px; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;">Web Workers</a><span style="background-color: transparent; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; line-height: 27px;">specification defines an API for spawning background scripts in your web application. Web Workers allow you to do things like fire up long-running scripts to handle computationally intensive tasks, but without blocking the UI or other scripts to handle user interactions. They're going to help put and end to that nasty 'unresponsive script' dialog that we've all come to love:</span></div>
<div>
<span style="background-color: transparent; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; line-height: 27px;"><br /></span>
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://2.bp.blogspot.com/-3mPsl2vvzG4/VUssptVKogI/AAAAAAAAQuw/mgc44xHHZsE/s1600/unresponsive_script.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://2.bp.blogspot.com/-3mPsl2vvzG4/VUssptVKogI/AAAAAAAAQuw/mgc44xHHZsE/s1600/unresponsive_script.gif" height="71" width="320" /></a></div>
<div class="separator" style="clear: both; text-align: center;">
<br /></div>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
Workers utilize thread-like message passing to achieve parallelism. They're perfect for keeping your UI refresh, performant, and responsive for users.</div>
<h3 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 22px; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
Types of Web Workers</h3>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
It's worth noting that the <a class="jive-link-external-small" href="http://www.whatwg.org/specs/web-workers/current-work/" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;">specification</a> discusses two kinds of Web Workers,<a class="jive-link-external-small" href="http://www.whatwg.org/specs/web-workers/current-work/#dedicated-workers-and-the-worker-interface" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;">Dedicated Workers</a> and <a class="jive-link-external-small" href="http://www.whatwg.org/specs/web-workers/current-work/#sharedworker" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;">Shared Workers</a>. This article will only cover dedicated workers and I'll refer to them as 'web workers' or 'workers' throughout.</div>
<h2 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 24px; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
Getting Started</h2>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
Web Workers run in an isolated thread. As a result, the code that they execute needs to be contained in a separate file. But before we do that, the first thing to do is create a new <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Worker</code> object in your main page. The constructor takes the name of the worker script:</div>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
<br /></div>
<pre class="prettyprint" style="background-color: #444444; border: 0px; color: white; font-family: 'Source Code Pro', monospace; font-size: 15px; margin-bottom: 2em; overflow-x: auto; padding: 1em 1em 1em 0px; vertical-align: baseline;"><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">var</span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> worker </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">new</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="typ" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Worker</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'task.js'</span></span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span></pre>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
If the specified file exists, the browser will spawn a new worker thread, which is downloaded asynchronously. The worker will not begin until the file has completely downloaded and executed. If the path to your worker returns an 404, the worker will fail silently.</div>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
After creating the worker, start it by calling the <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">postMessage()</code> method:</div>
<pre class="prettyprint" style="background-color: #444444; border: 0px; color: white; font-family: 'Source Code Pro', monospace; font-size: 15px; margin-bottom: 2em; overflow-x: auto; padding: 1em 1em 1em 0px; vertical-align: baseline;"><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">worker</span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">postMessage</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">();</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span></span><span style="border: 0px; font-family: inherit; font-style: italic; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">// Start the worker.</span></pre>
<h3 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 22px; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
Communicating with a Worker via Message Passing</h3>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
Communication between a work and its parent page is done using an event model and the <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">postMessage()</code> method. Depending on your browser/version,<code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">postMessage()</code> can accept either a string or JSON object as its single argument. The latest versions of the modern browsers support passing a JSON object.</div>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
Below is a example of using a string to pass 'Hello World' to a worker in doWork.js. The worker simply returns the message that is passed to it.</div>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
Main script:</div>
<pre class="prettyprint" style="background-color: #444444; border: 0px; color: white; font-family: 'Source Code Pro', monospace; font-size: 15px; margin-bottom: 2em; overflow-x: auto; padding: 1em 1em 1em 0px; vertical-align: baseline;"><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">var</span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> worker </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">new</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="typ" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Worker</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'doWork.js'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> worker</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">addEventListener</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'message'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">function</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">)</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">{</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> console</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">log</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'Worker said: '</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">data</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">},</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">false</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> worker</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">postMessage</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'Hello World'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span></span><span style="border: 0px; font-family: inherit; font-style: italic; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">// Send data to our worker.</span></pre>
<div>
<span style="border: 0px; font-family: inherit; font-style: italic; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"></span><br />
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: italic; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">doWork.js (the worker):</span></div>
<span style="border: 0px; font-family: inherit; font-style: italic; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">
</span>
<br />
<pre class="prettyprint" style="background-color: #444444; border: 0px; color: white; font-family: 'Source Code Pro', monospace; font-size: 15px; font-style: normal; margin-bottom: 2em; overflow-x: auto; padding: 1em 1em 1em 0px; vertical-align: baseline;"><span style="border: 0px; font-family: inherit; font-style: italic; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">self</span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">addEventListener</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'message'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">function</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">)</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">{</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">self</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">postMessage</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">data</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">},</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">false</span></span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span></span></pre>
<span style="border: 0px; font-family: inherit; font-style: italic; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">
</span>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: italic; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">When <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">postMessage()</code> is called from the main page, our worker handles that message by defining an <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">onmessage</code> handler for the <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">message</code> event. The message payload (in this case 'Hello World') is accessible in <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Event.data</code>. Although this particular example isn't very exciting, it demonstrates that <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">postMessage()</code> is also your means for passing data back to the main thread. Convenient!</span></div>
<span style="border: 0px; font-family: inherit; font-style: italic; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
Messages passed between the main page and workers are copied, not shared. For example, in the next example the 'msg' property of the JSON message is accessible in both locations. It appears that the object is being passed directly to the worker even though it's running in a separate, dedicated space. In actuality, what is happening is that the object is being serialized as it's handed to the worker, and subsequently, de-serialized on the other end. The page and worker do not share the same instance, so the end result is that a duplicate is created on each pass. Most browsers implement this feature by automatically JSON encoding/decoding the value on either end.</div>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
The following is a more complex example that passes messages using JSON objects.</div>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
Main script:</div>
<pre class="prettyprint" style="background-color: #444444; border: 0px; color: white; font-family: 'Source Code Pro', monospace; font-size: 15px; font-style: normal; margin-bottom: 2em; overflow-x: auto; padding: 1em 1em 1em 0px; vertical-align: baseline;"><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><button</span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="atn" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">onclick</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="atv" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">"</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">sayHI</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">()</span><span class="atv" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">"</span><span class="tag" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">></span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Say HI</span><span class="tag" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"></button></span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="tag" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><button</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="atn" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">onclick</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="atv" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">"</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">unknownCmd</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">()</span><span class="atv" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">"</span><span class="tag" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">></span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Send unknown command</span><span class="tag" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"></button></span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="tag" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><button</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="atn" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">onclick</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="atv" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">"</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">stop</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">()</span><span class="atv" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">"</span><span class="tag" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">></span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Stop worker</span><span class="tag" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"></button></span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="tag" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><output</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="atn" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">id</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="atv" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">"result"</span><span class="tag" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">></output></span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="tag" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><script></span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">function</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> sayHI</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">()</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">{</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> worker</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">postMessage</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">({</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'cmd'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">:</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'start'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'msg'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">:</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'Hi'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">});</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">}</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">function</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> stop</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">()</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">{</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="com" style="border: 0px; font-family: inherit; font-style: italic; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">// worker.terminate() from this script would also stop the worker.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">
worker</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">postMessage</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">({</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'cmd'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">:</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'stop'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'msg'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">:</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'Bye'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">});</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">}</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">function</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> unknownCmd</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">()</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">{</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">
worker</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">postMessage</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">({</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'cmd'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">:</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'foobard'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'msg'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">:</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'???'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">});</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">}</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">var</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> worker </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">new</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="typ" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Worker</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'doWork2.js'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">
worker</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">addEventListener</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'message'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">function</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">)</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">{</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> document</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">getElementById</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'result'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">).</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">textContent </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">data</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">;</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">},</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">false</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span></span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"></script></span></pre>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
doWork2.js:</div>
<pre class="prettyprint" style="background-color: #444444; border: 0px; color: white; font-family: 'Source Code Pro', monospace; font-size: 15px; font-style: normal; margin-bottom: 2em; overflow-x: auto; padding: 1em 1em 1em 0px; vertical-align: baseline;"><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">self</span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">addEventListener</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'message'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">function</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">)</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">{</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">var</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> data </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">data</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">;</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">switch</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">data</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">cmd</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">)</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">{</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">case</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'start'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">:</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">self</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">postMessage</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'WORKER STARTED: '</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">+</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> data</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">msg</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">break</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">;</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">case</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'stop'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">:</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">self</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">postMessage</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'WORKER STOPPED: '</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">+</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> data</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">msg </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">+</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'. (buttons will no longer work)'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">self</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">close</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">();</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="com" style="border: 0px; font-family: inherit; font-style: italic; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">// Terminates the worker.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">break</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">;</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">default</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">:</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">self</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">postMessage</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'Unknown command: '</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">+</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> data</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">msg</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">};</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">},</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">false</span></span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span></pre>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
<strong style="border: 0px; font-family: inherit; font-style: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Note</strong>: There are two ways to stop a worker: by calling <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">worker.terminate()</code> from the main page or by calling <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">self.close()</code> inside of the worker itself.</div>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; min-height: 8pt; padding: 0px; vertical-align: baseline;">
<br /></div>
<h2 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 24px; font-style: normal; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
Transferrable objects</h2>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
Most browsers implement the <a class="jive-link-external-small" href="http://updates.html5rocks.com/2011/09/Workers-ArrayBuffer" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;">structured cloning</a> algorithm, which allows you to pass more complex types in/out of Workers such as <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">File</code>,<code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Blob</code>, <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">ArrayBuffer</code>, and JSON objects. However, when passing these types of data using<code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">postMessage()</code>, a copy is still made. Therefore, if you're passing a large 50MB file (for example), there's a noticeable overhead in getting that file between the worker and the main thread.</div>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
Structured cloning is great, but a copy can take hundreds of milliseconds. To combat the perf hit, you can use <a class="jive-link-external-small" href="http://www.w3.org/html/wg/drafts/html/master/infrastructure.html#transferable-objects" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;">Transferable Objects</a>.</div>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
With Transferable Objects, data is transferred from one context to another. It is zero-copy, which vastly improves the performance of sending data to a Worker. Think of it as pass-by-reference if you're from the C/C++ world. However, unlike pass-by-reference, the 'version' from the calling context is no longer available once transferred to the new context. For example, when transferring an ArrayBuffer from your main app to Worker, the original <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">ArrayBuffer</code> is cleared and no longer usable. Its contents are (quiet literally) transferred to the Worker context.</div>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
To use transferrable objects, use a slightly different signature of <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">postMessage()</code>:</div>
<pre class="prettyprint" style="background-color: #444444; border: 0px; color: white; font-family: 'Source Code Pro', monospace; font-size: 15px; font-style: normal; margin-bottom: 2em; overflow-x: auto; padding: 1em 1em 1em 0px; vertical-align: baseline;"><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">worker</span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">postMessage</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">arrayBuffer</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">[</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">arrayBuffer</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">]);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">
window</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">postMessage</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">arrayBuffer</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> targetOrigin</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">[</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">arrayBuffer</span></span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">]);</span></pre>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
The worker case, the first argument is the data and the second is the list of items that should be transferred. The first argument doesn't have to be an <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">ArrayBuffer</code>by the way. For example, it can be a JSON object:</div>
<pre class="prettyprint" style="background-color: #444444; border: 0px; color: white; font-family: 'Source Code Pro', monospace; font-size: 15px; font-style: normal; margin-bottom: 2em; overflow-x: auto; padding: 1em 1em 1em 0px; vertical-align: baseline;"><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">worker</span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">postMessage</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">({</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">data</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">:</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> int8View</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> moreData</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">:</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> anotherBuffer</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">},</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">[</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">int8View</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">buffer</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> anotherBuffer</span></span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">]);</span></pre>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
The important point being: the second argument must be an array of<code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">ArrayBuffer</code>s. This is your list of transferrable items.</div>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
To see the speed improvement of transferrables, check out this <a class="jive-link-external-small" href="http://html5-demos.appspot.com/static/workers/transferables/index.html" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;">DEMO</a>. For more information on transferrables, see our <a class="jive-link-external-small" href="http://updates.html5rocks.com/2011/12/Transferable-Objects-Lightning-Fast" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;">HTML5Rock post</a>.</div>
<h2 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 24px; font-style: normal; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
The Worker Environment</h2>
<h3 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 22px; font-style: normal; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
Worker Scope</h3>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
In the context of a worker, both <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">self</code> and <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">this</code> reference the global scope for the worker. Thus, the previous example could also be written as:</div>
<pre class="prettyprint" style="background-color: #444444; border: 0px; color: white; font-family: 'Source Code Pro', monospace; font-size: 15px; font-style: normal; margin-bottom: 2em; overflow-x: auto; padding: 1em 1em 1em 0px; vertical-align: baseline;"><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">addEventListener</span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'message'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">function</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">)</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">{</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">var</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> data </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">data</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">;</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">switch</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">data</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">cmd</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">)</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">{</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">case</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'start'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">:</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> postMessage</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'WORKER STARTED: '</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">+</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> data</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">msg</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">break</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">;</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">case</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'stop'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">:</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">...</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">},</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">false</span></span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span></pre>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
Alternatively, you could set the <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">onmessage</code> event handler directly (though<code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">addEventListener</code> is always encouraged by JavaScript ninjas).</div>
<pre class="prettyprint" style="background-color: #444444; border: 0px; color: white; font-family: 'Source Code Pro', monospace; font-size: 15px; font-style: normal; margin-bottom: 2em; overflow-x: auto; padding: 1em 1em 1em 0px; vertical-align: baseline;"><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">onmessage </span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">function</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">)</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">{</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">var</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> data </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">data</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">;</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">...</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span></span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">};</span></pre>
<h3 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 22px; font-style: normal; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
Features Available to Workers</h3>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
Due to their multi-threaded behavior, web workers only has access to a subset of JavaScript's features:</div>
<ul style="background-color: transparent; border: 0px; color: #3d3d3d; font-family: 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px; font-style: normal; line-height: 19.5px; margin: 0px; padding: 0px 0px 0px 30px; vertical-align: baseline;">
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;">The <code style="border: 0px; font-family: 'Source Code Pro', monospace; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">navigator</code> object</li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;">The <code style="border: 0px; font-family: 'Source Code Pro', monospace; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">location</code> object (read-only)</li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;"><code style="border: 0px; font-family: 'Source Code Pro', monospace; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">XMLHttpRequest</code></li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;"><code style="border: 0px; font-family: 'Source Code Pro', monospace; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">setTimeout()/clearTimeout()</code> and<code style="border: 0px; font-family: 'Source Code Pro', monospace; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">setInterval()/clearInterval()</code></li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;">The <a class="jive-link-external-small" href="http://www.html5rocks.com/tutorials/appcache/beginner/" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;">Application Cache</a></li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;">Importing external scripts using the <code style="border: 0px; font-family: 'Source Code Pro', monospace; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">importScripts()</code> method</li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;"><a class="jive-link-external-small" href="http://www.html5rocks.com/en/tutorials/workers/basics/#toc-enviornment-subworkers" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;">Spawning other web workers</a></li>
</ul>
<div style="background-color: transparent; border: 0px; color: #3d3d3d; font-family: 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px; font-style: normal; line-height: 19.5px; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: inherit; font-weight: inherit; margin: 0.4em 0px 0.8em; padding: 0px; vertical-align: baseline;">Workers do NOT have access to:</span></div>
<ul style="background-color: transparent; border: 0px; color: #3d3d3d; font-family: 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px; font-style: normal; line-height: 19.5px; margin: 0px; padding: 0px 0px 0px 30px; vertical-align: baseline;">
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;">The DOM (it's not thread-safe)</li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;">The <code style="border: 0px; font-family: 'Source Code Pro', monospace; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">window</code> object</li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;">The <code style="border: 0px; font-family: 'Source Code Pro', monospace; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">document</code> object</li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;">The <code style="border: 0px; font-family: 'Source Code Pro', monospace; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">parent</code> object</li>
</ul>
<h3 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 22px; font-style: normal; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
Loading External Scripts</h3>
<div style="background-color: transparent; border: 0px; color: #3d3d3d; font-family: 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px; font-style: normal; line-height: 19.5px; padding: 0px; vertical-align: baseline;">
You can load external script files or libraries into a worker with the<code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">importScripts()</code> function. The method takes zero or more strings representing the filenames for the resources to import.</div>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
This example loads <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">script1.js</code> and <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">script2.js</code> into the worker:</div>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
worker.js:</div>
<pre class="prettyprint" style="background-color: #444444; border: 0px; color: white; font-family: 'Source Code Pro', monospace; font-size: 15px; font-style: normal; margin-bottom: 2em; overflow-x: auto; padding: 1em 1em 1em 0px; vertical-align: baseline;"><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">importScripts</span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'script1.js'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">
importScripts</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'script2.js'</span></span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span></pre>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
Which can also be written as a single import statement:</div>
<pre class="prettyprint" style="background-color: #444444; border: 0px; color: white; font-family: 'Source Code Pro', monospace; font-size: 15px; font-style: normal; margin-bottom: 2em; overflow-x: auto; padding: 1em 1em 1em 0px; vertical-align: baseline;"><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">importScripts</span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'script1.js'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'script2.js'</span></span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span></pre>
<h3 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 22px; font-style: normal; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
Subworkers</h3>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
Workers have the ability to spawn child workers. This is great for further breaking up large tasks at runtime. However, subworkers come with a few caveats:</div>
<ul style="background-color: transparent; border: 0px; color: #3d3d3d; font-family: 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px; font-style: normal; line-height: 19.5px; margin: 0px; padding: 0px 0px 0px 30px; vertical-align: baseline;">
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;">Subworkers must be hosted within the same origin as the parent page.</li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;">URIs within subworkers are resolved relative to their parent worker's location (as opposed to the main page).</li>
</ul>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
Keep in mind most browsers spawn separate processes for each worker. Before you go spawning a worker farm, be cautious about hogging too many of the user's system resources. One reason for this is that messages passed between main pages and workers are copied, not shared. See <a class="jive-link-external-small" href="http://www.html5rocks.com/en/tutorials/workers/basics/#toc-gettingstarted-workercomm" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;">Communicating with a Worker via Message Passing</a>.</div>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
For an sample of how to spawn a subworker, see <a class="jive-link-external-small" href="http://www.whatwg.org/specs/web-workers/current-work/#delegation" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;">the example</a> in the specification.</div>
<h2 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 24px; font-style: normal; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
Inline Workers</h2>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
What if you want to create your worker script on the fly, or create a self-contained page without having to create separate worker files? With<code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Blob()</code>, you can "inline" your worker in the same HTML file as your main logic by creating a URL handle to the worker code as a string:</div>
<pre class="prettyprint" style="background-color: #444444; border: 0px; color: white; font-family: 'Source Code Pro', monospace; font-size: 15px; font-style: normal; margin-bottom: 2em; overflow-x: auto; padding: 1em 1em 1em 0px; vertical-align: baseline;"><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">var</span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> blob </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">new</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="typ" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Blob</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">([</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">"onmessage = function(e) {
postMessage('msg from worker'); }"</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">]);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="com" style="border: 0px; font-family: inherit; font-style: italic; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">// Obtain a blob URL reference to our worker 'file'.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">var</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> blobURL </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> window</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">URL</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">createObjectURL</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">blob</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">var</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> worker </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">new</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="typ" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Worker</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">blobURL</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">
worker</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">onmessage </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">function</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">)</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">{</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="com" style="border: 0px; font-family: inherit; font-style: italic; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">// e.data == 'msg from worker'</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">};</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">
worker</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">postMessage</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">();</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span></span><span style="border: 0px; font-family: inherit; font-style: italic; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">// Start the worker.</span></pre>
<h3 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 22px; font-style: normal; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
Blob URLs</h3>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
The magic comes with the call to <a class="jive-link-external-small" href="http://dev.w3.org/2006/webapi/FileAPI/#dfn-createObjectURL" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;"><code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">window.URL.createObjectURL()</code></a>. This method creates a simple URL string which can be used to reference data stored in a DOM<code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">File</code> or <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Blob</code> object. For example:</div>
<pre class="prettyprint" style="background-color: #444444; border: 0px; color: white; font-family: 'Source Code Pro', monospace; font-size: 15px; font-style: normal; margin-bottom: 2em; overflow-x: auto; padding: 1em 1em 1em 0px; vertical-align: baseline;"><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">blob</span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">:</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">http</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">:</span></span><span style="border: 0px; font-family: inherit; font-style: italic; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">//localhost/c745ef73-ece9-46da-8f66-ebes574789b1</span></pre>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
Blob URLs are unique and last for the lifetime of your application (e.g. until the<code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">document</code> is unloaded). If you're creating many Blob URLs, it's a good idea to release references that are no longer needed. You can explicitly release a Blob URLs by passing it to<a class="jive-link-external-small" href="http://dev.w3.org/2006/webapi/FileAPI/#dfn-revokeObjectURL" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;"><code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">window.URL.revokeObjectURL()</code></a>:</div>
<pre class="prettyprint" style="background-color: #444444; border: 0px; color: white; font-family: 'Source Code Pro', monospace; font-size: 15px; font-style: normal; margin-bottom: 2em; overflow-x: auto; padding: 1em 1em 1em 0px; vertical-align: baseline;"><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">window</span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">URL</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">revokeObjectURL</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">blobURL</span></span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span></pre>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
In Chrome, there's a nice page to view all of the created blob URLs:<code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">chrome://blob-internals/</code>.</div>
<h3 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 22px; font-style: normal; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
Full Example</h3>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
Taking this one step further, we can get clever with how the worker's JS code is inlined in our page. This technique uses a <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><script></code> tag to define the worker:</div>
<pre class="prettyprint" style="background-color: #444444; border: 0px; color: white; font-family: 'Source Code Pro', monospace; font-size: 15px; font-style: normal; margin-bottom: 2em; overflow-x: auto; padding: 1em 1em 1em 0px; vertical-align: baseline;"><div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><!DOCTYPE html></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><html></span><br />
<span style="font-family: inherit; font-style: inherit; font-weight: inherit; line-height: 1.5em;"><head></span><br />
<span style="font-family: inherit; font-style: inherit; font-weight: inherit; line-height: 1.5em;"><meta charset="utf-8" /></span><br />
<span style="font-family: inherit; font-style: inherit; font-weight: inherit; line-height: 1.5em;"></head></span><br />
<span style="font-family: inherit; font-style: inherit; font-weight: inherit; line-height: 1.5em;"><body></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> <div id="log"></div></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> <script id="worker1" type="javascript/worker"></span><br />
<span style="font-family: inherit; font-style: inherit; font-weight: inherit; line-height: 1.5em;"> // This script won't be parsed by JS engines // because its type is javascript/worker. self.onmessage = function(e) { self.postMessage('msg from worker'); }; // Rest of your worker code goes here.</span><br />
<span style="font-family: inherit; font-style: inherit; font-weight: inherit; line-height: 1.5em;"> </script></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> <script></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> function log(msg) { // Use a fragment: browser will only render/reflow once.
var fragment = document.createDocumentFragment();
fragment.appendChild(document.createTextNode(msg));
fragment.appendChild(document.createElement('br'));
document.querySelector("#log").appendChild(fragment); }
var blob = new Blob([document.querySelector('#worker1').textContent]);
var worker = new Worker(window.URL.createObjectURL(blob));
worker.onmessage = function(e) { log("Received: " + e.data); }
worker.postMessage(); // Start the worker.</span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </script></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"></body></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"></html></span></div>
</pre>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
In my opinion, this new approach is a bit cleaner and more legible. It defines a script tag with <var style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">id="worker1"</var> and <var style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">type='javascript/worker'</var> (so the browser doesn't parse the JS). That code is extracted as a string using<code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">document.querySelector('#worker1').textContent</code> and passed to <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Blob()</code> to create the file.</div>
<h3 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 22px; font-style: normal; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
Loading External Scripts</h3>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
When using these techniques to inline your worker code, <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">importScripts()</code> will only work if you supply an absolute URI. If you attempt to pass a relative URI, the browser will complain with a security error. The reason being: the worker (now created from a blob URL) will be resolved with a <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">blob:</code> prefix, while your app will be running from a different (presumably <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><a class="jive-link-external-small" href="http://vox.sapient.com/" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-size: 16.2000007629395px; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;">http://</a></code>) scheme. Hence, the failure will be due to cross origin restrictions.</div>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
One way to utilize <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">importScripts()</code><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> in an inline worker is to "inject" the current url of your main script is running from by passing it to the inline worker and constructing the absolute URL manually. This will insure the external script is imported from the same origin. Assuming your main app is running from </span><a class="jive-link-external-small" href="http://example.com/index.html:" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;">http://example.com/index.html:</a></div>
<pre class="prettyprint" style="background-color: #444444; border: 0px; color: white; font-family: 'Source Code Pro', monospace; font-size: 15px; font-style: normal; margin-bottom: 2em; overflow-x: auto; padding: 1em 1em 1em 0px; vertical-align: baseline;"><div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">...</span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">script id</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">"worker2"</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> type</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">"javascript/worker"</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">></span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"></span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">self</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">onmessage </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">function</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">)</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">{</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">v</span></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">ar</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> data </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">data</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">;</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">if</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">data</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">url</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">)</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">{</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">var</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> url </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> data</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">url</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">href</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">;</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">var</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> index </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> url</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">indexOf</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'index.html'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"></span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">if</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">index </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">!=</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">-</span><span class="lit" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">1</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">)</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">{</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> url </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> url</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">substring</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="lit" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">0</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> index</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">}</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> importScripts</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">url </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">+</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'engine.js'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">}</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">...</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">};</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"></span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">/script> </span></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><script> var worker = new Worker(window.URL.createObjectURL(bb.getBlob())); </span></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">worker.postMessage(</span><strong style="border: 0px; font-family: inherit; font-style: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">{url: document.location}</span></strong><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">); </span></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"></</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">script</span></span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">></span></div>
</pre>
<h2 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 24px; font-style: normal; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
Handling Errors</h2>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
As with any JavaScript logic, you'll want to handle any errors that are thrown in your web workers. If an error occurs while a worker is executing, the an<code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">ErrorEvent</code> is fired. The interface contains three useful properties for figuring out what went wrong: <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">filename</code> - the name of the worker script that caused the error,<code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">lineno</code> - the line number where the error occurred, and <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">message</code> - a meaningful description of the error. Here is an example of setting up an <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">onerror</code> event handler to print the properties of the error:</div>
<pre class="prettyprint" style="background-color: #444444; border: 0px; color: white; font-family: 'Source Code Pro', monospace; font-size: 15px; font-style: normal; margin-bottom: 2em; overflow-x: auto; padding: 1em 1em 1em 0px; vertical-align: baseline;"><div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><output</span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="atn" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">id</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="atv" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">"error"</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="atn" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">style</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="atv" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">"</span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">color</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">:</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> red</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">;</span><span class="atv" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">"</span><span class="tag" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">></output></span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"></span><span class="tag" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><output</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="atn" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">id</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="atv" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">"result"</span><span class="tag" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">></output></span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"></span><span class="tag" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><script></span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">function</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> onError</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">)</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">{</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">document</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">getElementById</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'error'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">).</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">textContent </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">[</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'ERROR: Line '</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">lineno</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">' in '</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">filename</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">': '</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">message </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">].</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">join</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">''</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">}</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"></span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">function</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> onMsg</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">)</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">{</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> document</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">getElementById</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'result'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">).</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">textContent </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">data</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">;</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">}</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"></span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">var</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> worker </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">=</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">new</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="typ" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">Worker</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'workerWithError.js'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">worker</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">addEventListener</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'message'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> onMsg</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">false</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">worker</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">addEventListener</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'error'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> onError</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">false</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">worker</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">postMessage</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">();</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="com" style="border: 0px; font-family: inherit; font-style: italic; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">// Start worker without a message.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span></span></div>
<div style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; padding: 0px; vertical-align: baseline;">
<span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"></span></span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"></script></span></div>
</pre>
<div style="background-color: transparent; border: 0px; color: #3d3d3d; font-family: 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px; font-style: normal; line-height: 19.5px; min-height: 8pt; padding: 0px; vertical-align: baseline;">
<br /></div>
<div style="background-color: transparent; border: 0px; color: #3d3d3d; font-family: 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px; font-style: normal; line-height: 19.5px; min-height: 8pt; padding: 0px; vertical-align: baseline;">
<br /></div>
<pre class="prettyprint" style="background-color: #444444; border: 0px; color: white; font-family: 'Source Code Pro', monospace; font-size: 15px; font-style: normal; margin-bottom: 2em; overflow-x: auto; padding: 1em 1em 1em 0px; vertical-align: baseline;"><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">self</span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">addEventListener</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="str" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">'message'</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">,</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="kwd" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">function</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">e</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">)</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">{</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> postMessage</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">(</span><span class="lit" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">1</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">/</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">x</span><span class="pun" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">);</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span><span class="com" style="border: 0px; font-family: inherit; font-style: italic; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">// Intentional error.</span><span class="pln" style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;"> </span></span><span style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">};</span></pre>
<h2 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 24px; font-style: normal; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
A Word on Security</h2>
<h3 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 22px; font-style: normal; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
Restrictions with Local Access</h3>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
Due to Google Chrome's security restrictions, workers will not run locally (e.g. from<code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">file://</code>) in the latest versions of the browser. Instead, they fail silently! To run your app from the <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">file://</code> scheme, run Chrome with the <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">--allow-file-access-from-files</code> flag set. <strong style="border: 0px; font-family: inherit; font-style: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">NOTE</strong>: It is not recommended to run your primary browser with this flag set. It should only be used for testing purposes and not regular browsing.</div>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
Other browsers do not impose the same restriction.</div>
<h3 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 22px; font-style: normal; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
Same Origin Considerations</h3>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
Worker scripts must be external files with the same scheme as their calling page. Thus, you cannot load a script from a <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">data:</code> URL or<code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">javascript:</code> URL, and an<code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">https:</code> page cannot start worker scripts that begin with <code style="border: 0px; color: #333333; font-family: 'Source Code Pro', monospace; font-size: 0.9em; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px; vertical-align: baseline;">http:</code> URLs.</div>
<h2 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 24px; font-style: normal; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
Use Cases</h2>
<div style="background-color: transparent; border: 0px; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; margin-bottom: 0.8em; margin-top: 0.4em; padding: 0px; vertical-align: baseline;">
So what kind app would utilize web workers? Unfortunately, web workers are still relatively new and the majority of samples/tutorials out there involve computing prime numbers. Although that isn't very interesting, it's useful for understanding the concepts of web workers. Here are a few more ideas to get your brain churning:</div>
<ul style="background-color: transparent; border: 0px; color: #3d3d3d; font-family: 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px; font-style: normal; line-height: 19.5px; margin: 0px; padding: 0px 0px 0px 30px; vertical-align: baseline;">
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;">Prefetching and/or caching data for later use</li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;">Code syntax highlighting or other real-time text formatting</li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;">Spell checker</li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;">Analyzing video or audio data</li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;">Background I/O or polling of webservices</li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;">Processing large arrays or humungous JSON responses</li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;">Image filtering in <canvas></li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;">Updating many rows of a local web database</li>
</ul>
<h2 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 24px; font-style: normal; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
Demos</h2>
<ul style="background-color: transparent; border: 0px; color: #3d3d3d; font-family: 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px; font-style: normal; line-height: 19.5px; margin: 0px; padding: 0px 0px 0px 30px; vertical-align: baseline;">
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;">Example from <a class="jive-link-external-small" href="http://slides.html5rocks.com/#web-workers" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;">HTML5Rocks slides</a></li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;"><a class="jive-link-external-small" href="http://htmlfive.appspot.com/static/tracker1.html" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;">Motion tracker</a></li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;"><a class="jive-link-external-small" href="http://people.mozilla.com/~prouget/demos/worker_and_simulatedannealing/index.xhtml" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;">Simulated Annealing</a></li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;"><a class="jive-link-external-small" href="http://html5demos.com/worker" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;">HTML5demos sample</a></li>
</ul>
<h2 style="background-color: transparent; border: 0px; color: #333333; font-family: 'Open Sans'; font-size: 24px; font-style: normal; margin: 1.3em 0px 0.7em; padding: 0px; vertical-align: baseline;">
References</h2>
<ul style="background-color: transparent; border: 0px; color: #3d3d3d; font-family: 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif; font-size: 13px; font-style: normal; line-height: 19.5px; margin: 0px; padding: 0px 0px 0px 30px; vertical-align: baseline;">
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;"><a class="jive-link-external-small" href="http://www.whatwg.org/specs/web-workers/current-work/" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;">Web Workers</a> specification</li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;"><a class="jive-link-external-small" href="http://developer.mozilla.org/en/Using_web_workers" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;">"Using web workers"</a> from Mozilla Developer Network</li>
<li style="border: 0px; font-family: inherit; font-style: inherit; font-weight: inherit; list-style-type: inherit; margin: 0.5ex 0px; padding: 0px; vertical-align: baseline;"><a class="jive-link-external-small" href="http://dev.opera.com/articles/view/web-workers-rise-up/" rel="nofollow" style="border: 0px; color: #5073ad; font-family: inherit; font-style: inherit; font-weight: inherit; margin: 0px; padding: 0px calc(12px + 0.35ex) 0px 0px; text-decoration: none; vertical-align: baseline;">"Web Workers rise up!"</a> from Dev.Opera</li>
</ul>
</span></div>
<span style="background-color: transparent; color: #555555; font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 18px; line-height: 27px;"><br /></span></div>
</span></div>
Anonymoushttp://www.blogger.com/profile/12478702312334029028noreply@blogger.com0