Annotation of html5/workers/Overview.html, revision 1.308
1.281 ihickson 1: <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"><html lang="en-US-x-Hixie"><title>Web Workers</title><style type="text/css">
1.82 ihickson 2: pre { margin-left: 2em; white-space: pre-wrap; }
3: h2 { margin: 3em 0 1em 0; }
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1.300 ihickson 20: i, em { font-style: italic; }
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1.89 ihickson 25: @media screen { code { color: orangered; } code :link, code :visited { color: inherit; } }
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1.180 ihickson 30: table tbody th { text-align: left; }
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33:
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1.82 ihickson 46: pre.css { border: solid thin; background: #FFFFEE; color: black; padding: 0.5em 1em; }
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1.231 ihickson 48: dl.domintro { color: green; margin: 2em 0 2em 2em; padding: 0.5em 1em; border: none; background: #DDFFDD; }
1.82 ihickson 49: hr + dl.domintro, div.impl + dl.domintro { margin-top: 2.5em; margin-bottom: 1.5em; }
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1.121 ihickson 56: dl.triple { padding: 0 0 0 1em; }
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1.82 ihickson 60: .diff-old { text-decoration: line-through; color: silver; background: transparent; }
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63:
64: h2 { page-break-before: always; }
1.139 ihickson 65: h1, h2, h3, h4, h5, h6 { page-break-after: avoid; }
1.82 ihickson 66: h1 + h2, hr + h2.no-toc { page-break-before: auto; }
67:
1.267 ihickson 68: p > span:not([title=""]):not([class="XXX"]):not([class="impl"]):not([class="note"]),
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1.82 ihickson 70:
71: div.head { margin: 0 0 1em; padding: 1em 0 0 0; }
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73: div.head h1 { margin: 0; }
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1.212 ihickson 77: div.head p.copyright, div.head p.alt { font-size: x-small; font-style: oblique; margin: 0; }
1.82 ihickson 78:
79: body > .toc > li { margin-top: 1em; margin-bottom: 1em; }
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87: .brief li p { margin: 0; padding: 0; }
88:
1.137 ihickson 89: .category-list { margin-top: -0.75em; margin-bottom: 1em; line-height: 1.5; }
90: .category-list::before { content: '\21D2\A0'; font-size: 1.2em; font-weight: 900; }
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95:
1.82 ihickson 96: .XXX { color: #E50000; background: white; border: solid red; padding: 0.5em; margin: 1em 0; }
97: .XXX > :first-child { margin-top: 0; }
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1.158 ihickson 99: .annotation { border: solid thin black; background: #0C479D; color: white; position: relative; margin: 8px 0 20px 0; }
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1.82 ihickson 104: .note { color: green; background: transparent; font-family: sans-serif; }
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1.300 ihickson 107: .note em, .warning em, .note i, .warning i { font-style: normal; }
1.82 ihickson 108: p.note, div.note { padding: 0.5em 2em; }
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1.262 ihickson 119: .bookkeeping dt { margin: 0.5em 2em 0; }
120: .bookkeeping dd { margin: 0 3em 0.5em; }
1.82 ihickson 121:
122: h4 { position: relative; z-index: 3; }
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1.88 ihickson 125: background: #EEEEFF;
1.82 ihickson 126: color: black;
127: margin: 0 0 1em 0.15em;
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1.88 ihickson 129: border-left: solid #9999FF 0.25em;
1.82 ihickson 130: position: relative;
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1.88 ihickson 140: background: #EEEEFF;
1.82 ihickson 141: content: ' ';
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1.88 ihickson 143: border-color: #9999FF;
1.82 ihickson 144: border-width: 0.25em;
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146:
1.156 ihickson 147: .example { display: block; color: #222222; background: #FCFCFC; border-left: double; margin-left: 2em; padding-left: 1em; }
148: td > .example:only-child { margin: 0 0 0 0.1em; }
1.82 ihickson 149:
1.131 ihickson 150: ul.domTree, ul.domTree ul { padding: 0 0 0 1em; margin: 0; }
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162: ul.domTree .t10 code { color: teal; }
163:
1.225 ihickson 164: body.dfnEnabled dfn { cursor: pointer; }
165: .dfnPanel {
166: display: inline;
167: position: absolute;
168: z-index: 10;
169: height: auto;
170: width: auto;
171: padding: 0.5em 0.75em;
172: font: small sans-serif, Droid Sans Fallback;
173: background: #DDDDDD;
174: color: black;
175: border: outset 0.2em;
176: }
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181: .dfnPanel li { list-style-position: inside; }
182:
1.207 ihickson 183: #configUI { position: absolute; z-index: 20; top: 10em; right: 1em; width: 11em; font-size: small; }
184: #configUI p { margin: 0.5em 0; padding: 0.3em; background: #EEEEEE; color: black; border: inset thin; }
185: #configUI p label { display: block; }
186: #configUI #updateUI, #configUI .loginUI { text-align: center; }
187: #configUI input[type=button] { display: block; margin: auto; }
1.260 ihickson 188:
1.268 ihickson 189: fieldset { margin: 1em; padding: 0.5em 1em; }
190: fieldset > legend + * { margin-top: 0; }
1.266 ihickson 191: fieldset > :last-child { margin-bottom: 0; }
1.268 ihickson 192: fieldset p { margin: 0.5em 0; }
1.266 ihickson 193:
1.271 ihickson 194: </style><link href="http://www.w3.org/StyleSheets/TR/W3C-ED" rel="stylesheet" type="text/css"><script type="text/javascript">
195: function getCookie(name) {
196: var params = location.search.substr(1).split("&");
197: for (var index = 0; index < params.length; index++) {
198: if (params[index] == name)
199: return "1";
200: var data = params[index].split("=");
201: if (data[0] == name)
202: return unescape(data[1]);
203: }
204: var cookies = document.cookie.split("; ");
205: for (var index = 0; index < cookies.length; index++) {
206: var data = cookies[index].split("=");
207: if (data[0] == name)
208: return unescape(data[1]);
209: }
210: return null;
211: }
1.283 ihickson 212: </script><div class="head" id="head">
1.115 ihickson 213: <p><a href="http://www.w3.org/"><img alt="W3C" height="48" src="http://www.w3.org/Icons/w3c_home" width="72"></a></p>
1.271 ihickson 214:
1.54 ihickson 215: <h1>Web Workers</h1>
1.281 ihickson 216:
1.308 ! ihickson 217: <h2 class="no-num no-toc" id="editor-s-draft-29-september-2011">Editor's Draft 29 September 2011</h2>
1.218 ihickson 218: <dl><dt>Latest Published Version:</dt>
1.115 ihickson 219: <dd><a href="http://www.w3.org/TR/workers/">http://www.w3.org/TR/workers/</a></dd>
1.109 ihickson 220: <dt>Latest Editor's Draft:</dt>
1.260 ihickson 221: <dd><a class="latest-link" href="http://dev.w3.org/html5/workers/">http://dev.w3.org/html5/workers/</a></dd>
1.284 ihickson 222:
1.2 ihickson 223: <dt>Previous Versions:</dt>
1.279 ihickson 224: <dd><a href="http://www.w3.org/TR/2011/WD-workers-20110310/">http://www.w3.org/TR/2011/WD-workers-20110310/</a></dd>
225: <dd><a href="http://www.w3.org/TR/2011/WD-workers-20110208/">http://www.w3.org/TR/2011/WD-workers-20110208/</a></dd>
1.198 ihickson 226: <dd><a href="http://www.w3.org/TR/2009/WD-workers-20091029/">http://www.w3.org/TR/2009/WD-workers-20091029/</a></dd>
1.279 ihickson 227: <dd><a href="http://www.w3.org/TR/2009/WD-workers-20090423/">http://www.w3.org/TR/2009/WD-workers-20090423/</a></dd>
1.117 ihickson 228: <!-- :ZZZ -->
1.271 ihickson 229: <dt>Editor:</dt>
1.115 ihickson 230: <dd><a href="mailto:ian@hixie.ch">Ian Hickson</a>, Google, Inc.</dd>
1.155 ihickson 231: </dl><p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a>
1.285 ihickson 232: © 2011 <a href="http://www.w3.org/"><abbr title="World Wide
1.155 ihickson 233: Web Consortium">W3C</abbr></a><sup>®</sup> (<a href="http://www.csail.mit.edu/"><abbr title="Massachusetts
1.297 ihickson 234: Institute of Technology">MIT</abbr></a>, <a href="http://www.ercim.eu/"><abbr title="European Research
1.115 ihickson 235: Consortium for Informatics and Mathematics">ERCIM</abbr></a>, <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C
236: <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
237: <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
238: and <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document
1.81 ihickson 239: use</a> rules apply.</p>
1.201 ihickson 240:
1.254 ihickson 241:
1.252 ihickson 242: <!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
1.255 ihickson 243: <p class="alt">The bulk of the text of this specification is also
1.254 ihickson 244: available in the WHATWG <a href="http://www.whatwg.org/specs/web-apps/current-work/complete.html#workers">Web Applications 1.0</a> specification, under a license that permits
245: reuse of the specification text.</p>
1.252 ihickson 246: <!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
247:
1.254 ihickson 248:
1.155 ihickson 249: </div><hr class="top"><h2 class="no-num no-toc" id="abstract">Abstract</h2><p>This specification defines an API that allows Web application
1.81 ihickson 250: authors to spawn background workers running scripts in parallel to
251: their main page. This allows for thread-like operation with
1.281 ihickson 252: message-passing as the coordination mechanism.<h2 class="no-num no-toc" id="status-of-this-document">Status of This document</h2><p><em>This section describes the status of this document at the
1.81 ihickson 253: time of its publication. Other documents may supersede this
1.297 ihickson 254: document. A list of current W3C publications and the
255:
256: most recently formally published <!-- DO NOT CHANGE THIS BACK TO THE STANDARD BOILERPLATE, AS IT IS INACCURATE -->
257:
258: revision of this technical report can be found in the <a href="http://www.w3.org/TR/">W3C technical reports index</a> at
259: http://www.w3.org/TR/.</em></p><p>If you wish to make comments regarding this document in a manner
1.271 ihickson 260: that is tracked by the W3C, please submit them via using <a href="http://www.w3.org/Bugs/Public/enter_bug.cgi?product=HTML%20WG">our
261: public bug database</a>. If you do not have an account then you can
262: enter feedback using this form:<form action="http://www.whatwg.org/specs/web-apps/current-work/file-spam.cgi" method="post">
263: <fieldset><legend>Feedback Comments</legend>
264: <input name="id" type="hidden" value="top"><input name="component" type="hidden" value="Web Workers (editor: Ian Hickson)"><input name="response" type="hidden" value="html"><p><label for="feedbackBox">Please enter your feedback, carefully
265: indicating the title of the section for which you are submitting
266: feedback, quoting the text that's wrong today if appropriate. If
267: you're suggesting a new feature, it's really important to say
268: <em>what</em> the problem you're trying to solve is. That's more
269: important than the solution, in fact.</label></p>
270: <p><textarea cols="79" id="feedbackBox" name="text" rows="10"></textarea></p>
271: <p class="note">Please don't use section numbers as these tend to
272: change rapidly and make your feedback harder to understand.</p>
273: <script type="text/javascript">
1.287 ihickson 274: function checkFeedbackForm(form) {
275: if (form.elements.text.value.match(/^ *</)) {
276: alert('Please don\'t start your feedback with an angle bracket, instead explain what topic your feedback is about first.');
277: return true;
278: } else if (form.elements.text.value.match(/ [^ ]+ [^ ]+ [^ ]+ [^ ]+ /)) {
279: if (form.elements.text.value.match(/^Please enter your feedback, carefully/)) {
280: alert('Please enter your feedback, explaining what is wrong, and without repeating the instructions. Thanks!');
281: return true;
282: } else if (form.elements.text.value.match(/ [^ ]+ [^ ]+ [^ ]+ [^ ]+ /)) {
283: form.action = "http://www.whatwg.org/specs/web-apps/current-work/file-bug.cgi";
284: return true;
285: } else {
286: alert('Please include significantly more detail about exactly what problem you are trying to solve.');
287: return false;
288: }
289: }
290: }
1.271 ihickson 291: </script><p>
1.277 ihickson 292: <input onclick="return checkFeedbackForm(form)" type="submit" value="Submit feedback"><small>(Note: Your IP address and user agent will be publicly recorded for spam prevention purposes.)</small>
1.271 ihickson 293: </p>
294: </fieldset></form><p>You can also e-mail feedback to <a href="mailto:public-webapps@w3.org">public-webapps@w3.org</a> (<a href="mailto:public-webapps-request@w3.org?subject=subscribe">subscribe</a>,
295: <a href="http://lists.w3.org/Archives/Public/public-webapps/">archives</a>),
1.115 ihickson 296: or <a href="mailto:whatwg@whatwg.org">whatwg@whatwg.org</a> (<a href="http://lists.whatwg.org/listinfo.cgi/whatwg-whatwg.org">subscribe</a>,
297: <a href="http://lists.whatwg.org/pipermail/whatwg-whatwg.org/">archives</a>).
1.281 ihickson 298: All feedback is welcome.</p><p>Implementors should be aware that this specification is not
1.81 ihickson 299: stable. <strong>Implementors who are not taking part in the
300: discussions are likely to find the specification changing out from
301: under them in incompatible ways.</strong> Vendors interested in
302: implementing this specification before it eventually reaches the
303: Candidate Recommendation stage should join the aforementioned
1.271 ihickson 304: mailing lists and take part in the discussions.<div id="multipage-common">
1.281 ihickson 305: </div><p>The latest
1.271 ihickson 306: stable version of the editor's draft of this specification is always
307: available on <a href="http://dev.w3.org/html5/workers/">the W3C CVS server</a>
308: and in the <a href="http://svn.whatwg.org/webapps/">WHATWG
309: Subversion repository</a>. The <a href="http://www.whatwg.org/specs/web-apps/current-work/complete.html">latest
310: editor's working copy</a> (which may contain unfinished text in the
311: process of being prepared) contains the latest draft text of this
312: specification (amongst others). For more details, please see the <a href="http://wiki.whatwg.org/wiki/FAQ#What_are_the_various_versions_of_the_spec.3F">WHATWG
313: FAQ</a>.<p>Notifications of changes to this specification are sent along
314: with notifications of changes to related specifications using the
315: following mechanisms:<dl><dt>E-mail notifications of changes</dt>
316: <dd>Commit-Watchers mailing list (complete source diffs): <a href="http://lists.whatwg.org/listinfo.cgi/commit-watchers-whatwg.org">http://lists.whatwg.org/listinfo.cgi/commit-watchers-whatwg.org</a></dd>
317: <dt>Browsable version-control record of all changes:</dt>
318: <dd>CVSWeb interface with side-by-side diffs: <a href="http://dev.w3.org/cvsweb/html5/">http://dev.w3.org/cvsweb/html5/</a></dd>
319: <dd>Annotated summary with unified diffs: <a href="http://html5.org/tools/web-apps-tracker">http://html5.org/tools/web-apps-tracker</a></dd>
320: <dd>Raw Subversion interface: <code>svn checkout http://svn.whatwg.org/webapps/</code></dd>
321: </dl><p>The W3C <a href="http://www.w3.org/2008/webapps/">Web Applications
1.81 ihickson 322: Working Group</a> is the W3C working group responsible for this
323: specification's progress along the W3C Recommendation track.
1.308 ! ihickson 324: This specification is the 29 September 2011 Editor's Draft.
1.281 ihickson 325: </p><p>This document was produced by a group operating under the <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5
1.115 ihickson 326: February 2004 W3C Patent Policy</a>. W3C maintains a <a href="http://www.w3.org/2004/01/pp-impl/42538/status" rel="disclosure">public list of
1.81 ihickson 327: any patent disclosures</a> made in connection with the deliverables
328: of the group; that page also includes instructions for disclosing a
329: patent. An individual who has actual knowledge of a patent which the
1.115 ihickson 330: individual believes contains <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential
331: Claim(s)</a> must disclose the information in accordance with <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section
1.252 ihickson 332: 6 of the W3C Patent Policy</a>.<h2 class="no-num no-toc" id="contents">Table of Contents</h2>
1.115 ihickson 333: <ol class="toc">
334: <li><a href="#introduction"><span class="secno">1 </span>Introduction</a>
1.81 ihickson 335: <ol>
1.115 ihickson 336: <li><a href="#scope"><span class="secno">1.1 </span>Scope</a></li>
1.303 ihickson 337: <li><a href="#examples"><span class="secno">1.2 </span>Examples</a>
1.81 ihickson 338: <ol>
1.115 ihickson 339: <li><a href="#a-background-number-crunching-worker"><span class="secno">1.2.1 </span>A background number-crunching worker</a></li>
340: <li><a href="#a-worker-for-updating-a-client-side-database"><span class="secno">1.2.2 </span>A worker for updating a client-side database</a></li>
341: <li><a href="#worker-used-for-background-i-o"><span class="secno">1.2.3 </span>Worker used for background I/O</a></li>
1.238 ihickson 342: <li><a href="#shared-workers-introduction"><span class="secno">1.2.4 </span>Shared workers introduction</a></li>
343: <li><a href="#shared-state-using-a-shared-worker"><span class="secno">1.2.5 </span>Shared state using a shared worker</a></li>
1.303 ihickson 344: <li><a href="#delegation"><span class="secno">1.2.6 </span>Delegation</a></ol></li>
345: <li><a href="#tutorials"><span class="secno">1.3 </span>Tutorials</a>
346: <ol>
347: <li><a href="#creating-a-dedicated-worker"><span class="secno">1.3.1 </span>Creating a dedicated worker</a></li>
348: <li><a href="#communicating-with-a-dedicated-worker"><span class="secno">1.3.2 </span>Communicating with a dedicated worker</a></li>
349: <li><a href="#shared-workers"><span class="secno">1.3.3 </span>Shared workers</a></ol></ol></li>
1.148 ihickson 350: <li><a href="#conformance-requirements"><span class="secno">2 </span>Conformance requirements</a>
1.82 ihickson 351: <ol>
1.148 ihickson 352: <li><a href="#dependencies"><span class="secno">2.1 </span>Dependencies</a></ol></li>
353: <li><a href="#terminology"><span class="secno">3 </span>Terminology</a></li>
354: <li><a href="#infrastructure"><span class="secno">4 </span>Infrastructure</a>
355: <ol>
1.301 ihickson 356: <li><a href="#dependencies-0"><span class="secno">4.1 </span>Dependencies</a></li>
357: <li><a href="#the-global-scope"><span class="secno">4.2 </span>The global scope</a>
1.81 ihickson 358: <ol>
1.301 ihickson 359: <li><a href="#the-workerglobalscope-abstract-interface"><span class="secno">4.2.1 </span>The <code>WorkerGlobalScope</code> abstract interface</a></li>
360: <li><a href="#dedicated-workers-and-the-dedicatedworkerglobalscope-interface"><span class="secno">4.2.2 </span>Dedicated workers and the <code>DedicatedWorkerGlobalScope</code> interface</a></li>
361: <li><a href="#shared-workers-and-the-sharedworkerglobalscope-interface"><span class="secno">4.2.3 </span>Shared workers and the <code>SharedWorkerGlobalScope</code> interface</a></ol></li>
362: <li><a href="#origins-of-workers"><span class="secno">4.3 </span>Origins of workers</a></li>
363: <li><a href="#the-event-loop"><span class="secno">4.4 </span>The event loop</a></li>
364: <li><a href="#the-worker-s-lifetime"><span class="secno">4.5 </span>The worker's lifetime</a></li>
365: <li><a href="#processing-model"><span class="secno">4.6 </span>Processing model</a></li>
366: <li><a href="#runtime-script-errors"><span class="secno">4.7 </span>Runtime script errors</a></li>
367: <li><a href="#creating-workers"><span class="secno">4.8 </span>Creating workers</a>
1.81 ihickson 368: <ol>
1.301 ihickson 369: <li><a href="#the-abstractworker-abstract-interface"><span class="secno">4.8.1 </span>The <code>AbstractWorker</code> abstract interface</a></li>
370: <li><a href="#dedicated-workers-and-the-worker-interface"><span class="secno">4.8.2 </span>Dedicated workers and the <code>Worker</code> interface</a></li>
371: <li><a href="#shared-workers-and-the-sharedworker-interface"><span class="secno">4.8.3 </span>Shared workers and the <code>SharedWorker</code> interface</a></ol></ol></li>
1.148 ihickson 372: <li><a href="#apis-available-to-workers"><span class="secno">5 </span>APIs available to workers</a>
1.81 ihickson 373: <ol>
1.148 ihickson 374: <li><a href="#importing-scripts-and-libraries"><span class="secno">5.1 </span>Importing scripts and libraries</a></li>
1.210 ihickson 375: <li><a href="#the-workernavigator-object"><span class="secno">5.2 </span>The <code>WorkerNavigator</code> object</a></li>
1.272 ihickson 376: <li><a href="#interface-objects-and-constructors"><span class="secno">5.3 </span>Interface objects and constructors</a></li>
377: <li><a href="#worker-locations"><span class="secno">5.4 </span>Worker locations</a></ol></li>
1.115 ihickson 378: <li><a class="no-num" href="#references">References</a></li>
379: <li><a class="no-num" href="#acknowledgements">Acknowledgements</a></ol>
1.281 ihickson 380: <hr><h2 id="introduction"><span class="secno">1 </span>Introduction</h2><h3 id="scope"><span class="secno">1.1 </span>Scope</h3><p><i>This section is non-normative.</i><p>This specification defines an API for running scripts in the
1.155 ihickson 381: background independently of any user interface scripts.<p>This allows for long-running scripts that are not interrupted by
1.81 ihickson 382: scripts that respond to clicks or other user interactions, and
383: allows long tasks to be executed without yielding to keep the page
1.155 ihickson 384: responsive.<p>Workers (as these background scripts are called herein) are
1.81 ihickson 385: relatively heavy-weight, and are not intended to be used in large
386: numbers. For example, it would be inappropriate to launch one worker
387: for each pixel of a four megapixel image. The examples below show
1.155 ihickson 388: some appropriate uses of workers.<p>Generally, workers are expected to be long-lived, have a high
1.303 ihickson 389: start-up performance cost, and a high per-instance memory cost.<h3 id="examples"><span class="secno">1.2 </span>Examples</h3><p><i>This section is non-normative.</i><p>There are a variety of uses that workers can be put to. The
1.155 ihickson 390: following subsections show various examples of this use.<h4 id="a-background-number-crunching-worker"><span class="secno">1.2.1 </span>A background number-crunching worker</h4><p><i>This section is non-normative.</i><p>The simplest use of workers is for performing a computationally
391: expensive task without interrupting the user interface.<p>In this example, the main document spawns a worker to
392: (naïvely) compute prime numbers, and progressively displays the
393: most recently found prime number.<p>The main page is as follows:<pre><!DOCTYPE HTML>
1.81 ihickson 394: <html>
395: <head>
396: <title>Worker example: One-core computation</title>
397: </head>
398: <body>
399: <p>The highest prime number discovered so far is: <output id="result"></output></p>
400: <script>
1.50 ihickson 401: var worker = new Worker('worker.js');
402: worker.onmessage = function (event) {
1.54 ihickson 403: document.getElementById('result').textContent = event.data;
1.29 ihickson 404: };
1.81 ihickson 405: </script>
406: </body>
1.155 ihickson 407: </html></pre><p>The <code title="dom-Worker"><a href="#dom-worker">Worker()</a></code> constructor call
1.115 ihickson 408: creates a worker and returns a <code><a href="#worker">Worker</a></code> object
1.81 ihickson 409: representing that worker, which is used to communicate with the
1.177 ihickson 410: worker. That object's <code title="handler-Worker-onmessage"><a href="#handler-worker-onmessage">onmessage</a></code> event handler allows the code to receive messages from the worker.<p>The worker itself is as follows:<pre>var n = 1;
1.29 ihickson 411: search: while (true) {
412: n += 1;
413: for (var i = 2; i <= Math.sqrt(n); i += 1)
414: if (n % i == 0)
415: continue search;
416: // found a prime!
1.50 ihickson 417: postMessage(n);
1.155 ihickson 418: }</pre><p>The bulk of this code is simply an unoptimized search for a prime
1.295 ihickson 419: number. The <code title="dom-DedicatedWorkerGlobalScope-postMessage"><a href="#dom-dedicatedworkerglobalscope-postmessage">postMessage()</a></code>
420: method is used to send a message back to the page when a prime is
421: found.<p><a href="http://www.whatwg.org/demos/workers/primes/page.html">View this example online</a>.<h4 id="a-worker-for-updating-a-client-side-database"><span class="secno">1.2.2 </span>A worker for updating a client-side database</h4><p><i>This section is non-normative.</i><p>In this example, the main document spawns a worker whose only
1.81 ihickson 422: task is to listen for notifications from the server, and, when
423: appropriate, either add or remove data from the client-side
1.155 ihickson 424: database.<p>Since no communication occurs between the worker and the main
425: page, the main page can start the worker by just doing:<pre><script>
1.50 ihickson 426: new Worker('worker.js');
1.155 ihickson 427: </script></pre><p>The worker itself is as follows:<pre>var server = new WebSocket('ws://whatwg.org/database');
1.42 ihickson 428: var database = openDatabase('demobase', '1.0', 'Demo Database', 10240);
1.31 ihickson 429: server.onmessage = function (event) {
430: // data is in the format "command key value"
1.54 ihickson 431: var data = event.data.split(' ');
1.31 ihickson 432: switch (data[0]) {
433: case '+':
434: database.transaction(function(tx) {
435: tx.executeSql('INSERT INTO pairs (key, value) VALUES (?, ?)', data[1], data[2]);
436: });
437: case '-':
438: database.transaction(function(tx) {
439: tx.executeSql('DELETE FROM pairs WHERE key=? AND value=?', data[1], data[2]);
440: });
441: }
1.155 ihickson 442: };</pre><p>This connects to the server using the <code>WebSocket</code>
1.81 ihickson 443: mechanism and opens the local database (which, we presume, has been
444: created earlier). The worker then just listens for messages from the
445: server and acts on them as appropriate, forever (or until the main
1.155 ihickson 446: page is closed).<p><a href="http://www.whatwg.org/demos/workers/database-updater/page.html">View
1.81 ihickson 447: this example online</a>. (This example will not actually function,
448: since the server does not actually exist and the database is not
1.155 ihickson 449: created by this sample code.)<h4 id="worker-used-for-background-i-o"><span class="secno">1.2.3 </span>Worker used for background I/O</h4><p><i>This section is non-normative.</i><p>In this example, the main document uses two workers, one for
1.81 ihickson 450: fetching stock updates for at regular intervals, and one for
1.155 ihickson 451: fetching performing search queries that the user requests.<p>The main page is as follows:<pre><!DOCTYPE HTML>
1.81 ihickson 452: <html>
453: <head>
454: <title>Worker example: Stock ticker</title>
455: <script>
1.33 ihickson 456: // TICKER
457: var symbol = 'GOOG'; // default symbol to watch
1.50 ihickson 458: var ticker = new Worker('ticker.js');
1.33 ihickson 459:
460: // SEARCHER
1.50 ihickson 461: var searcher = new Worker('searcher.js');
1.33 ihickson 462: function search(query) {
1.50 ihickson 463: searcher.postMessage(query);
1.33 ihickson 464: }
465:
466: // SYMBOL SELECTION UI
467: function select(newSymbol) {
468: symbol = newSymbol;
1.50 ihickson 469: ticker.postMessage(symbol);
1.33 ihickson 470: }
1.81 ihickson 471: </script>
472: </head>
1.122 ihickson 473: <body onload="search('')">
1.81 ihickson 474: <p><output id="symbol"></output> <output id="value"></output></p>
475: <script>
1.50 ihickson 476: ticker.onmessage = function (event) {
1.54 ihickson 477: var data = event.data.split(' ');
1.33 ihickson 478: document.getElementById('symbol').textContent = data[0];
479: document.getElementById('value').textContent = data[1];
480: };
1.50 ihickson 481: ticker.postMessage(symbol);
1.81 ihickson 482: </script>
1.122 ihickson 483: <p><label>Search: <input type="text" autofocus oninput="search(this.value)"></label></p>
1.81 ihickson 484: <ul id="results"></ul>
485: <script>
1.50 ihickson 486: searcher.onmessage = function (event) {
1.54 ihickson 487: var data = event.data.split(' ');
1.33 ihickson 488: var results = document.getElementById('results');
489: while (results.hasChildNodes()) // clear previous results
490: results.removeChild(results.firstChild);
491: for (var i = 0; i < data.length; i += 1) {
492: // add a list item with a button for each result
493: var li = document.createElement('li');
494: var button = document.createElement('button');
495: button.value = data[i];
496: button.type = 'button';
497: button.onclick = function () { select(this.value); };
498: button.textContent = data[i];
499: li.appendChild(button);
500: results.appendChild(li);
501: }
502: };
1.81 ihickson 503: </script>
504: <p>(The data in this example is not real. Try searching for "Google" or "Apple".)</p>
505: </body>
1.155 ihickson 506: </html></pre><p>The two workers use a common library for performing the actual
507: network calls. This library is as follows:<pre>function get(url) {
1.50 ihickson 508: try {
509: var xhr = new XMLHttpRequest();
510: xhr.open('GET', url, false);
511: xhr.send();
512: return xhr.responseText;
513: } catch (e) {
514: return ''; // turn all errors into empty results
515: }
1.155 ihickson 516: }</pre><p>The stock updater worker is as follows:<pre>importScripts('io.js');
1.33 ihickson 517: var timer;
518: var symbol;
519: function update() {
1.50 ihickson 520: postMessage(symbol + ' ' + get('stock.cgi?' + symbol));
1.33 ihickson 521: timer = setTimeout(update, 10000);
522: }
1.50 ihickson 523: onmessage = function (event) {
1.33 ihickson 524: if (timer)
525: clearTimeout(timer);
1.54 ihickson 526: symbol = event.data;
1.33 ihickson 527: update();
1.155 ihickson 528: };</pre><p>The search query worker is as follows:<pre>importScripts('io.js');
1.50 ihickson 529: onmessage = function (event) {
1.54 ihickson 530: postMessage(get('search.cgi?' + event.data));
1.238 ihickson 531: };</pre><p><a href="http://www.whatwg.org/demos/workers/stocks/page.html">View this example online</a>.<h4 id="shared-workers-introduction"><span class="secno">1.2.4 </span>Shared workers introduction</h4><p><i>This section is non-normative.</i><p>This section introduces shared workers using a Hello World
532: example. Shared workers use slightly different APIs, since each
533: worker can have multiple connections.<p>This first example shows how you connect to a worker and how a
534: worker can send a message back to the page when it connects to
1.239 ihickson 535: it. Received messages are displayed in a log.<p>Here is the HTML page:<pre><!DOCTYPE HTML>
536: <title>Shared workers: demo 1</title>
537: <pre id="log">Log:</pre>
538: <script>
539: var worker = new SharedWorker('test.js');
540: var log = document.getElementById('log');
541: worker.port.onmessage = function(e) { // note: not worker.onmessage!
542: log.textContent += '\n' + e.data;
543: }
544: </script>
545: </pre><p>Here is the JavaScript worker:<pre>onconnect = function(e) {
546: var port = e.ports[0];
547: port.postMessage('Hello World!');
548: }
1.259 ihickson 549: </pre><p><a href="http://www.whatwg.org/demos/workers/shared/001/test.html">View this example online</a>.<hr><p>This second example extends the first one by changing two things:
1.238 ihickson 550: first, messages are received using <code title="">addEventListener()</code> instead of an <span title="event
551: handler IDL attributes">event handler IDL attribute</span>, and
552: second, a message is sent <em>to</em> the worker, causing the worker
553: to send another message in return. Received messages are again
1.239 ihickson 554: displayed in a log.<p>Here is the HTML page:<pre><!DOCTYPE HTML>
1.240 ihickson 555: <title>Shared workers: demo 2</title>
1.239 ihickson 556: <pre id="log">Log:</pre>
557: <script>
558: var worker = new SharedWorker('test.js');
559: var log = document.getElementById('log');
1.240 ihickson 560: worker.port.addEventListener('message', function(e) {
1.239 ihickson 561: log.textContent += '\n' + e.data;
1.240 ihickson 562: }, false);
563: worker.port.start(); // note: need this when using addEventListener
564: worker.port.postMessage('ping');
1.239 ihickson 565: </script>
566: </pre><p>Here is the JavaScript worker:<pre>onconnect = function(e) {
567: var port = e.ports[0];
568: port.postMessage('Hello World!');
1.240 ihickson 569: port.onmessage = function(e) {
570: port.postMessage('pong'); // not e.ports[0].postMessage!
571: // e.target.postMessage('pong'); would work also
572: }
1.239 ihickson 573: }
1.259 ihickson 574: </pre><p><a href="http://www.whatwg.org/demos/workers/shared/002/test.html">View this example online</a>.<hr><p>Finally, the example is extended to show how two pages can
1.238 ihickson 575: connect to the same worker; in this case, the second page is merely
576: in an <code>iframe</code> on the first page, but the same principle
577: would apply to an entirely separate page in a separate
1.239 ihickson 578: <span>top-level browsing context</span>.<p>Here is the outer HTML page:<pre><!DOCTYPE HTML>
579: <title>Shared workers: demo 3</title>
580: <pre id="log">Log:</pre>
581: <script>
582: var worker = new SharedWorker('test.js');
583: var log = document.getElementById('log');
584: worker.port.addEventListener('message', function(e) {
585: log.textContent += '\n' + e.data;
586: }, false);
587: worker.port.start();
588: worker.port.postMessage('ping');
589: </script>
590: <iframe src="inner.html"></iframe>
591: </pre><p>Here is the inner HTML page:<pre><!DOCTYPE HTML>
592: <title>Shared workers: demo 3 inner frame</title>
593: <pre id=log>Inner log:</pre>
594: <script>
595: var worker = new SharedWorker('test.js');
596: var log = document.getElementById('log');
597: worker.port.onmessage = function(e) {
598: log.textContent += '\n' + e.data;
599: }
600: </script>
601: </pre><p>Here is the JavaScript worker:<pre>var count = 0;
602: onconnect = function(e) {
603: count += 1;
604: var port = e.ports[0];
605: port.postMessage('Hello World! You are connection #' + count);
606: port.onmessage = function(e) {
607: port.postMessage('pong');
608: }
609: }
1.259 ihickson 610: </pre><p><a href="http://www.whatwg.org/demos/workers/shared/003/test.html">View this example online</a>.<h4 id="shared-state-using-a-shared-worker"><span class="secno">1.2.5 </span>Shared state using a shared worker</h4><p><i>This section is non-normative.</i><p>In this example, multiple windows (viewers) can be opened that
1.81 ihickson 611: are all viewing the same map. All the windows share the same map
612: information, with a single worker coordinating all the viewers. Each
613: viewer can move around independently, but if they set any data on
1.155 ihickson 614: the map, all the viewers are updated.<p>The main page isn't interesting, it merely provides a way to open
615: the viewers:<pre><!DOCTYPE HTML>
1.81 ihickson 616: <html>
617: <head>
618: <title>Workers example: Multiviewer</title>
619: <script>
1.36 ihickson 620: function openViewer() {
621: window.open('viewer.html');
622: }
1.81 ihickson 623: </script>
624: </head>
625: <body>
626: <p><button type=button onclick="openViewer()">Open a new
627: viewer</button></p>
628: <p>Each viewer opens in a new window. You can have as many viewers
629: as you like, they all view the same data.</p>
630: </body>
1.155 ihickson 631: </html></pre><p>The viewer is more involved:<pre><!DOCTYPE HTML>
1.81 ihickson 632: <html>
633: <head>
634: <title>Workers example: Multiviewer viewer</title>
635: <script>
1.50 ihickson 636: var worker = new SharedWorker('worker.js', 'core');
1.36 ihickson 637:
638: // CONFIGURATION
639: function configure(event) {
1.54 ihickson 640: if (event.data.substr(0, 4) != 'cfg ') return;
641: var name = event.data.substr(4).split(' ', 1);
1.36 ihickson 642: // update display to mention our name is name
643: document.getElementsByTagName('h1')[0].textContent += ' ' + name;
644: // no longer need this listener
1.43 ihickson 645: worker.port.removeEventListener('message', configure, false);
1.36 ihickson 646: }
1.53 ihickson 647: worker.port.addEventListener('message', configure, false);
1.36 ihickson 648:
649: // MAP
650: function paintMap(event) {
1.54 ihickson 651: if (event.data.substr(0, 4) != 'map ') return;
652: var data = event.data.substr(4).split(',');
1.36 ihickson 653: // display tiles data[0] .. data[8]
654: var canvas = document.getElementById('map');
655: var context = canvas.getContext('2d');
656: for (var y = 0; y < 3; y += 1) {
657: for (var x = 0; x < 3; x += 1) {
658: var tile = data[y * 3 + x];
659: if (tile == '0')
660: context.fillStyle = 'green';
661: else
662: context.fillStyle = 'maroon';
663: fillRect(x * 50, y * 50, 50, 50);
664: }
665: }
666: }
1.53 ihickson 667: worker.port.addEventListener('message', paintMap, false);
1.36 ihickson 668:
669: // PUBLIC CHAT
670: function updatePublicChat(event) {
1.54 ihickson 671: if (event.data.substr(0, 4) != 'txt ') return;
672: var name = event.data.substr(4).split(' ', 1);
673: var message = event.data.substr(4 + length(name) + 1);
1.81 ihickson 674: // display "<name> message" in public chat
1.36 ihickson 675: var dialog = document.getElementById('public');
676: var dt = document.createElement('dt');
677: dt.textContent = name;
678: dialog.appendChild(dt);
679: var dd = document.createElement('dd');
680: dd.textContent = message;
681: dialog.appendChild(dd);
682: }
1.53 ihickson 683: worker.port.addEventListener('message', updatePublicChat, false);
1.36 ihickson 684:
685: // PRIVATE CHAT
686: function startPrivateChat(event) {
1.54 ihickson 687: if (event.data.substr(0, 4) != 'msg ') return;
688: var name = event.data.substr(4).split(' ', 1);
1.84 ihickson 689: var port = event.ports[0];
1.36 ihickson 690: // display a private chat UI
691: var ul = document.getElementById('private');
692: var li = document.createElement('li');
693: var h3 = document.createElement('h3');
694: h3.textContent = 'Private chat with ' + name;
695: li.appendChild(h3);
696: var dialog = document.createElement('dialog');
697: var addMessage = function(name, message) {
698: var dt = document.createElement('dt');
699: dt.textContent = name;
700: dialog.appendChild(dt);
701: var dd = document.createElement('dd');
702: dd.textContent = message;
703: dialog.appendChild(dd);
704: };
705: port.onmessage = function (event) {
1.54 ihickson 706: addMessage(name, event.data);
1.36 ihickson 707: };
708: li.appendChild(dialog);
709: var form = document.createElement('form');
710: var p = document.createElement('p');
711: var input = document.createElement('input');
712: input.size = 50;
713: p.appendChild(input);
714: p.appendChild(document.createTextNode(' '));
715: var button = document.createElement('button');
716: button.textContent = 'Post';
717: p.appendChild(button);
718: form.onsubmit = function () {
719: port.postMessage(input.value);
720: addMessage('me', input.value);
721: input.value = '';
722: return false;
723: };
724: form.appendChild(p);
725: li.appendChild(form);
726: }
1.53 ihickson 727: worker.port.addEventListener('message', startPrivateChat, false);
1.188 ihickson 728:
729: worker.port.start();
1.81 ihickson 730: </script>
731: </head>
732: <body>
733: <h1>Viewer</h1>
734: <h2>Map</h2>
735: <p><canvas id="map" height=150 width=150></canvas></p>
736: <p>
737: <button type=button onclick="worker.port.postMessage('mov left')">Left</button>
738: <button type=button onclick="worker.port.postMessage('mov up')">Up</button>
739: <button type=button onclick="worker.port.postMessage('mov down')">Down</button>
740: <button type=button onclick="worker.port.postMessage('mov right')">Right</button>
741: <button type=button onclick="worker.port.postMessage('set 0')">Set 0</button>
742: <button type=button onclick="worker.port.postMessage('set 1')">Set 1</button>
743: </p>
744: <h2>Public Chat</h2>
745: <dialog id="public"></dialog>
746: <form onsubmit="worker.port.postMessage('txt ' + message.value); message.value = ''; return false;">
747: <p>
748: <input type="text" name="message" size="50">
749: <button>Post</button>
750: </p>
751: </form>
752: <h2>Private Chat</h2>
753: <ul id="private"></ul>
754: </body>
755: </html>
1.155 ihickson 756: </pre><p>There are several key things worth noting about the way the
757: viewer is written.<p><strong>Multiple listeners</strong>. Instead of a single message
1.81 ihickson 758: processing function, the code here attaches multiple event
759: listeners, each one performing a quick check to see if it is
760: relevant for the message. In this example it doesn't make much
761: difference, but if multiple authors wanted to collaborate using a
762: single port to communicate with a worker, it would allow for
763: independent code instead of changes having to all be made to a
1.155 ihickson 764: single event handling function.<p>Registering event listeners in this way also allows you to
1.81 ihickson 765: unregister specific listeners when you are done with them, as is
766: done with the <code title="">configure()</code> method in this
1.155 ihickson 767: example.<p>Finally, the worker:<pre>
768: var nextName = 0;
1.36 ihickson 769: function getNextName() {
770: // this could use more friendly names
771: // but for now just return a number
772: return nextName++;
773: }
774:
775: var map = [
776: [0, 0, 0, 0, 0, 0, 0],
777: [1, 1, 0, 1, 0, 1, 1],
778: [0, 1, 0, 1, 0, 0, 0],
779: [0, 1, 0, 1, 0, 1, 1],
780: [0, 0, 0, 1, 0, 0, 0],
781: [1, 0, 0, 1, 1, 1, 1],
782: [1, 1, 0, 1, 1, 0, 1],
783: ];
784:
785: function wrapX(x) {
786: if (x < 0) return wrapX(x + map[0].length);
1.81 ihickson 787: if (x >= map[0].length) return wrapX(x - map[0].length);
1.36 ihickson 788: return x;
789: }
790:
791: function wrapY(y) {
792: if (y < 0) return wrapY(y + map.length);
1.81 ihickson 793: if (y >= map[0].length) return wrapY(y - map.length);
1.36 ihickson 794: return y;
795: }
796:
1.50 ihickson 797: function sendMapData(callback) {
1.36 ihickson 798: var data = '';
799: for (var y = viewer.y-1; y <= viewer.y+1; y += 1) {
800: for (var x = viewer.x-1; x <= viewer.x+1; x += 1) {
801: if (data != '')
802: data += ',';
803: data += map[y][x];
804: }
805: }
1.50 ihickson 806: callback('map ' + data);
1.36 ihickson 807: }
808:
809: var viewers = {};
810: onconnect = function (event) {
1.84 ihickson 811: event.ports[0]._name = getNextName();
812: event.ports[0]._data = { port: event.port, x: 0, y: 0, };
813: viewers[event.ports[0]._name] = event.port._data;
814: event.ports[0].postMessage('cfg ' + name);
815: event.ports[0].onmessage = getMessage;
816: sendMapData(event.ports[0].postMessage);
1.36 ihickson 817: };
818:
819: function getMessage(event) {
1.54 ihickson 820: switch (event.data.substr(0, 4)) {
1.36 ihickson 821: case 'mov ':
1.54 ihickson 822: var direction = event.data.substr(4);
1.36 ihickson 823: var dx = 0;
824: var dy = 0;
825: switch (direction) {
826: case 'up': dy = -1; break;
827: case 'down': dy = 1; break;
828: case 'left': dx = -1; break;
829: case 'right': dx = 1; break;
830: }
831: event.target._data.x = wrapX(event.target._data.x + dx);
832: event.target._data.y = wrapY(event.target._data.y + dy);
1.50 ihickson 833: sendMapData(event.target.postMessage);
1.36 ihickson 834: break;
835: case 'set ':
1.54 ihickson 836: var value = event.data.substr(4);
1.36 ihickson 837: map[event.target._data.y][event.target._data.x] = value;
838: for (var viewer in viewers)
1.50 ihickson 839: sendMapData(viewers[viewer].port.postMessage);
1.36 ihickson 840: break;
841: case 'txt ':
842: var name = event.target._name;
1.54 ihickson 843: var message = event.data.substr(4);
1.36 ihickson 844: for (var viewer in viewers)
845: viewers[viewer].port.postMessage('txt ' + name + ' ' + message);
846: break;
847: case 'msg ':
848: var party1 = event._data;
1.54 ihickson 849: var party2 = viewers[event.data.substr(4).split(' ', 1)];
1.36 ihickson 850: if (party2) {
851: var channel = new MessageChannel();
1.84 ihickson 852: party1.port.postMessage('msg ' + party2.name, [channel.port1]);
853: party2.port.postMessage('msg ' + party1.name, [channel.port2]);
1.36 ihickson 854: }
855: break;
856: }
1.155 ihickson 857: }</pre><p><strong>Connecting to multiple pages</strong>. The script uses
1.115 ihickson 858: the <code title="handler-SharedWorkerGlobalScope-onconnect"><a href="#handler-sharedworkerglobalscope-onconnect">onconnect</a></code>
1.155 ihickson 859: event listener to listen for multiple connections.<p><strong>Direct channels</strong>. When the worker receives a
1.81 ihickson 860: "msg" message from one viewer naming another viewer, it sets up a
861: direct connection between the two, so that the two viewers can
862: communicate directly without the worker having to proxy all the
1.238 ihickson 863: messages.<p><a href="http://www.whatwg.org/demos/workers/multiviewer/page.html">View this example online</a>.<h4 id="delegation"><span class="secno">1.2.6 </span>Delegation</h4><p><i>This section is non-normative.</i><p>With multicore CPUs becoming prevalent, one way to obtain better
1.81 ihickson 864: performance is to split computationally expensive tasks amongst
865: multiple workers. In this example, a computationally expensive task
866: that is to be performed for every number from 1 to 10,000,000 is
1.155 ihickson 867: farmed out to ten subworkers.<p>The main page is as follows, it just reports the result:<pre><!DOCTYPE HTML>
1.81 ihickson 868: <html>
869: <head>
1.203 ihickson 870: <title>Worker example: Multicore computation</title>
1.81 ihickson 871: </head>
872: <body>
1.203 ihickson 873: <p>Result: <output id="result"></output></p>
1.81 ihickson 874: <script>
1.50 ihickson 875: var worker = new Worker('worker.js');
876: worker.onmessage = function (event) {
1.54 ihickson 877: document.getElementById('result').textContent = event.data;
1.40 ihickson 878: };
1.81 ihickson 879: </script>
880: </body>
1.155 ihickson 881: </html></pre><p>The worker itself is as follows:<pre>// settings
1.40 ihickson 882: var num_workers = 10;
883: var items_per_worker = 1000000;
884:
885: // start the workers
886: var result = 0;
887: var pending_workers = num_workers;
888: for (var i = 0; i < num_workers; i += 1) {
1.50 ihickson 889: var worker = new Worker('core.js');
890: worker.postMessage(i * items_per_worker);
891: worker.postMessage((i+1) * items_per_worker);
892: worker.onmessage = storeResult;
1.40 ihickson 893: }
894:
895: // handle the results
896: function storeResult(event) {
1.54 ihickson 897: result += 1*event.data;
1.40 ihickson 898: pending_workers -= 1;
899: if (pending_workers <= 0)
1.50 ihickson 900: postMessage(result); // finished!
1.155 ihickson 901: }</pre><p>It consists of a loop to start the subworkers, and then a handler
902: that waits for all the subworkers to respond.<p>The subworkers are implemented as follows:<pre>var start;
1.41 ihickson 903: onmessage = getStart;
1.40 ihickson 904: function getStart(event) {
1.54 ihickson 905: start = 1*event.data;
1.40 ihickson 906: onmessage = getEnd;
907: }
908:
909: var end;
910: function getEnd(event) {
1.54 ihickson 911: end = 1*event.data;
1.40 ihickson 912: onmessage = null;
1.66 ihickson 913: work();
1.40 ihickson 914: }
915:
1.66 ihickson 916: function work() {
1.40 ihickson 917: var result = 0;
918: for (var i = start; i < end; i += 1) {
919: // perform some complex calculation here
920: result += 1;
921: }
1.50 ihickson 922: postMessage(result);
923: close();
1.155 ihickson 924: }</pre><p>They receive two numbers in two events, perform the computation
1.81 ihickson 925: for the range of numbers thus specified, and then report the result
1.303 ihickson 926: back to the parent.<p><a href="http://www.whatwg.org/demos/workers/multicore/page.html">View this example online</a>.</p><h3 id="tutorials"><span class="secno">1.3 </span>Tutorials</h3><h4 id="creating-a-dedicated-worker"><span class="secno">1.3.1 </span>Creating a dedicated worker</h4><p><i>This section is non-normative.</i><p>Creating a worker requires a URL to a JavaScript file. The <code title="dom-Worker"><a href="#dom-worker">Worker()</a></code> constructor is invoked with the
927: URL to that file as its only argument; a worker is then created and
928: returned:<pre>var worker = new Worker('helper.js');</pre><h4 id="communicating-with-a-dedicated-worker"><span class="secno">1.3.2 </span>Communicating with a dedicated worker</h4><p><i>This section is non-normative.</i><p>Dedicated workers use <code><a href="#messageport">MessagePort</a></code> objects behind the
929: scenes, and thus support all the same features, such as sending
930: structured data, transferring binary data, and transferring other
931: ports.<p>To receive messages from a dedicated worker, use the <code title="handler-worker-onmessage"><a href="#handler-worker-onmessage">onmessage</a></code> <span title="event
932: handler IDL attributes">event handler IDL attribute</span> on the
933: <code><a href="#worker">Worker</a></code> object:<pre>worker.onmessage = function (event) { ... };</pre><p>You can also use the <code title="dom-EventTarget-addEventListener">addEventListener()</code> method.<p class="note">The implicit <code><a href="#messageport">MessagePort</a></code> used by
934: dedicated workers has its <span>port message queue</span> implicitly
935: enabled when it is created, so there is no equivanet to the
936: <code><a href="#messageport">MessagePort</a></code> interface's <code title="dom-MessagePort-start">start()</code> method on the
937: <code><a href="#worker">Worker</a></code> interface.<p>To <em>send</em> data to a worker, use the <code title="dom-Worker-postMessage"><a href="#dom-worker-postmessage">postMessage()</a></code> method.
938: Structured data can be sent over this communication channel. To send
939: <code>ArrayBuffer</code> objects efficiently (by transferring them
940: rather than cloning them), list them in an array in the second
941: argument.<pre>worker.postMessage({
942: operation: 'find-edges',
943: input: buffer, // an ArrayBuffer object
944: threshold: 0.6,
945: }, [buffer]);</pre><p>To receive a message inside the worker, the <code title="handler-DedicatedWorkerGlobalScope-onmessage"><a href="#handler-dedicatedworkerglobalscope-onmessage">onmessage</a></code>
946: <span title="event handler IDL attributes">event handler IDL
947: attribute</span> is used.<pre>onmessage = function (event) { ... };</pre><p>You can again also use the <code title="dom-EventTarget-addEventListener">addEventListener()</code>
948: method.<p>In either case, the data is provided in the event object's <code title="dom-MessageEvent-data">data</code> attribute.<p>To send messages back, you again use <code title="dom-DedicatedWorkerGlobalScope-postMessage"><a href="#dom-dedicatedworkerglobalscope-postmessage">postMessage()</a></code>.
949: It supports the structured data in the same manner.<pre>postMessage(event.data.input, [event.data.input]); // transfer the buffer back</pre><h4 id="shared-workers"><span class="secno">1.3.3 </span>Shared workers</h4><p><i>This section is non-normative.</i><p>Shared workers are identified in one of two ways: either by the
950: URL of the script used to create it, or by explicit name. When
951: created by name, the URL used by the first page to create the worker
952: with that name is the URL of the script that will be used for that
953: worker. This allows multiple applications on a domain to all use a
954: single shared worker to provide a common service, without the
955: applications having to keep track of a common URL for the script
956: used to provide the service.<p class="note">In either case, shared workers are scoped by
957: <span>origin</span>. Two different sites using the same names will
958: not collide.<p>Creating shared workers is done using the <code title="dom-SharedWorker"><a href="#dom-sharedworker">SharedWorker()</a></code> constructor. This
959: constructor takes the URL to the script to use for its first
960: argument, and the name of the worker, if any, as the second
961: argument.<pre>var worker = new SharedWorker('service.js');</pre><p>Communicating with shared workers is done with explicit
962: <code><a href="#messageport">MessagePort</a></code> objects. The object returned by the <code title="dom-SharedWorker"><a href="#dom-sharedworker">SharedWorker()</a></code> constructor holds a
963: reference to the port on its <code title="dom-SharedWorker-port"><a href="#dom-sharedworker-port">port</a></code> attribute.<pre>worker.port.onmessage = function (event) { ... };
964: worker.port.postMessage('some message');
965: worker.port.postMessage({ foo: 'structured'; bar: ['data', 'also', 'possible']});</pre><p>Inside the shared worker, new clients of the worker are announced
966: using the <code title="event-connect">connect</code> event. The port
967: for the new client is given by the event object's <code title="dom-messageevent-ports">ports</code> array as its first (and
968: only) value.<pre>onconnect = function (event) {
969: var newPort = event.ports[0];
970: // set up a listener
971: newPort.onmessage = function (event) { ... };
972: // send a message back to the port
973: newPort.postMessage('ready!'); // can also send structured data, of course
974: };</pre><h2 id="conformance-requirements"><span class="secno">2 </span>Conformance requirements</h2><p>All diagrams, examples, and notes in this specification are
1.81 ihickson 975: non-normative, as are all sections explicitly marked non-normative.
1.281 ihickson 976: Everything else in this specification is normative.<p>The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
1.81 ihickson 977: "OPTIONAL" in the normative parts of this document are to be
978: interpreted as described in RFC2119. For readability, these words do
1.155 ihickson 979: not appear in all uppercase letters in this specification. <a href="#refsRFC2119">[RFC2119]</a><p>Requirements phrased in the imperative as part of algorithms
1.81 ihickson 980: (such as "strip any leading space characters" or "return false and
981: abort these steps") are to be interpreted with the meaning of the
982: key word ("must", "should", "may", etc) used in introducing the
1.155 ihickson 983: algorithm.<p>Some conformance requirements are phrased as requirements on
1.81 ihickson 984: attributes, methods or objects. Such requirements are to be
1.155 ihickson 985: interpreted as requirements on user agents.<p>Conformance requirements phrased as algorithms or specific steps
1.81 ihickson 986: may be implemented in any manner, so long as the end result is
987: equivalent. (In particular, the algorithms defined in this
988: specification are intended to be easy to follow, and not intended to
1.155 ihickson 989: be performant.)<p>The only conformance class defined by this specification is user
990: agents.<p>User agents may impose implementation-specific limits on
1.81 ihickson 991: otherwise unconstrained inputs, e.g. to prevent denial of service
992: attacks, to guard against running out of memory, or to work around
1.229 ihickson 993: platform-specific limitations.<p>When support for a feature is disabled (e.g. as an emergency
994: measure to mitigate a security problem, or to aid in development, or
995: for performance reasons), user agents must act as if they had no
996: support for the feature whatsoever, and as if the feature was not
997: mentioned in this specification. For example, if a particular
998: feature is accessed via an attribute in a Web IDL interface, the
999: attribute itself would be omitted from the objects that implement
1000: that interface — leaving the attribute on the object but
1001: making it return null or throw an exception is insufficient.<h3 id="dependencies"><span class="secno">2.1 </span>Dependencies</h3><p>This specification relies on several other underlying
1.226 ihickson 1002: specifications.<dl><dt>HTML</dt>
1.49 ihickson 1003:
1.81 ihickson 1004: <dd>
1.49 ihickson 1005:
1.226 ihickson 1006: <p>Many fundamental concepts from HTML are used by this
1007: specification. <a href="#refsHTML">[HTML]</a></p>
1.49 ihickson 1008:
1.81 ihickson 1009: </dd>
1.1 ihickson 1010:
1.81 ihickson 1011: <dt>WebIDL</dt>
1.1 ihickson 1012:
1013: <dd>
1014:
1.81 ihickson 1015: <p>The IDL blocks in this specification use the semantics of the
1.153 ihickson 1016: WebIDL specification. <a href="#refsWEBIDL">[WEBIDL]</a></p>
1.1 ihickson 1017:
1.81 ihickson 1018: </dd>
1.1 ihickson 1019:
1.155 ihickson 1020: </dl><h2 id="terminology"><span class="secno">3 </span>Terminology</h2><p>The construction "a <code title="">Foo</code> object", where
1.81 ihickson 1021: <code title="">Foo</code> is actually an interface, is sometimes
1022: used instead of the more accurate "an object implementing the
1.155 ihickson 1023: interface <code title="">Foo</code>".<p>The term DOM is used to refer to the API set made available to
1.81 ihickson 1024: scripts in Web applications, and does not necessarily imply the
1025: existence of an actual <code>Document</code> object or of any other
1026: <code>Node</code> objects as defined in the DOM Core
1.171 ihickson 1027: specifications. <a href="#refsDOMCORE">[DOMCORE]</a><p>An IDL attribute is said to be <em>getting</em> when its value is
1.81 ihickson 1028: being retrieved (e.g. by author script), and is said to be
1.155 ihickson 1029: <em>setting</em> when a new value is assigned to it.<p>The term "JavaScript" is used to refer to ECMA262, rather than
1.103 ihickson 1030: the official term ECMAScript, since the term JavaScript is more
1.155 ihickson 1031: widely known. <a href="#refsECMA262">[ECMA262]</a><h2 id="infrastructure"><span class="secno">4 </span>Infrastructure</h2><p>There are two kinds of workers; dedicated workers, and shared
1.81 ihickson 1032: workers. Dedicated workers, once created, and are linked to their
1033: creator; but message ports can be used to communicate from a
1034: dedicated worker to multiple other browsing contexts or
1035: workers. Shared workers, on the other hand, are named, and once
1036: created any script running in the same <span>origin</span> can
1.301 ihickson 1037: obtain a reference to that worker and communicate with it.<h3 id="dependencies-0"><span class="secno">4.1 </span>Dependencies</h3><p>The <dfn id="messageport"><code>MessagePort</code></dfn> interface is defined in
1.302 ihickson 1038: the HTML specification. <a href="#refsHTML">[HTML]</a><h3 id="the-global-scope"><span class="secno">4.2 </span>The global scope</h3><p>The global scope is the "inside" of a worker.<h4 id="the-workerglobalscope-abstract-interface"><span class="secno">4.2.1 </span>The <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> abstract interface</h4><pre class="idl">interface <dfn id="workerglobalscope">WorkerGlobalScope</dfn> : <span>EventTarget</span> {
1.115 ihickson 1039: readonly attribute <a href="#workerglobalscope">WorkerGlobalScope</a> <a href="#dom-workerglobalscope-self" title="dom-WorkerGlobalScope-self">self</a>;
1040: readonly attribute <a href="#workerlocation">WorkerLocation</a> <a href="#dom-workerglobalscope-location" title="dom-WorkerGlobalScope-location">location</a>;
1041:
1042: void <a href="#dom-workerglobalscope-close" title="dom-WorkerGlobalScope-close">close</a>();
1.308 ! ihickson 1043: [TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-workerglobalscope-onerror" title="handler-WorkerGlobalScope-onerror">onerror</a>;
! 1044: [TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-workerglobalscope-onoffline" title="handler-WorkerGlobalScope-onoffline">onoffline</a>;
! 1045: [TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-workerglobalscope-ononline" title="handler-WorkerGlobalScope-ononline">ononline</a>;
1.150 ihickson 1046: };
1.302 ihickson 1047: <a href="#workerglobalscope">WorkerGlobalScope</a> implements <a href="#workerutils">WorkerUtils</a>;</pre><p>The <dfn id="dom-workerglobalscope-self" title="dom-WorkerGlobalScope-self"><code>self</code></dfn> attribute
1.155 ihickson 1048: must return the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object itself.<p>The <dfn id="dom-workerglobalscope-location" title="dom-WorkerGlobalScope-location"><code>location</code></dfn>
1.115 ihickson 1049: attribute must return the <code><a href="#workerlocation">WorkerLocation</a></code> object created
1050: for the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object when the worker was
1.81 ihickson 1051: created. It represents the <span>absolute URL</span> of the script
1.155 ihickson 1052: that was used to initialize the worker, after any redirects.<hr><p>When a script invokes the <dfn id="dom-workerglobalscope-close" title="dom-WorkerGlobalScope-close"><code>close()</code></dfn>
1.123 ihickson 1053: method on a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, the user agent
1.155 ihickson 1054: must run the following steps (atomically):<ol><li><p>Discard any <span title="concept-task">tasks</span> that
1.123 ihickson 1055: have been added to the <span>event loop</span>'s <span title="task
1056: queue">task queues</span>.</p>
1057:
1.81 ihickson 1058:
1.115 ihickson 1059: <li><p>Set the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's
1060: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag to
1.123 ihickson 1061: true. (This prevents any further tasks from being queued.)</li>
1.81 ihickson 1062:
1.177 ihickson 1063: </ol><p>The following are the <span>event handlers</span> (and their
1064: corresponding <span title="event handler event type">event handler
1065: event types</span>) that must be supported, as IDL attributes, by
1066: objects implementing the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1067: interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.281 ihickson 1068: <tbody><tr><td><dfn id="handler-workerglobalscope-onerror" title="handler-WorkerGlobalScope-onerror"><code>onerror</code></dfn> <td> <code title="event-error">error</code>
1.289 ihickson 1069: <tr><td><dfn id="handler-workerglobalscope-onoffline" title="handler-WorkerGlobalScope-onoffline"><code>onoffline</code></dfn> <td> <code title="event-offline">offline</code>
1070: <tr><td><dfn id="handler-workerglobalscope-ononline" title="handler-WorkerGlobalScope-ononline"><code>ononline</code></dfn> <td> <code title="event-online">online</code>
1.209 ihickson 1071: </table><hr><p>The <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> interface must not exist if
1072: the interface's <span>relevant namespace object</span> is a
1.301 ihickson 1073: <code>Window</code> object. <a href="#refsWEBIDL">[WEBIDL]</a><h4 id="dedicated-workers-and-the-dedicatedworkerglobalscope-interface"><span class="secno">4.2.2 </span>Dedicated workers and the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> interface</h4><pre class="idl">[Supplemental, NoInterfaceObject]
1.150 ihickson 1074: interface <dfn id="dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</dfn> : <a href="#workerglobalscope">WorkerGlobalScope</a> {
1.308 ! ihickson 1075: void <a href="#dom-dedicatedworkerglobalscope-postmessage" title="dom-DedicatedWorkerGlobalScope-postMessage">postMessage</a>(any message, optional sequence<<span>Transferable</span>> transfer); [TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-dedicatedworkerglobalscope-onmessage" title="handler-DedicatedWorkerGlobalScope-onmessage">onmessage</a>;
1.155 ihickson 1076: };</pre><p><code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> objects act as if they
1.301 ihickson 1077: had an implicit <code><a href="#messageport">MessagePort</a></code> associated with them. This
1.81 ihickson 1078: port is part of a channel that is set up when the worker is created,
1079: but it is not exposed. This object must never be garbage collected
1.155 ihickson 1080: before the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object.<p>All messages received by that port must immediately be retargeted
1.281 ihickson 1081: at the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object.<p>The <dfn id="dom-dedicatedworkerglobalscope-postmessage" title="dom-DedicatedWorkerGlobalScope-postMessage"><code>postMessage()</code></dfn> method on
1.115 ihickson 1082: <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> objects must act as if, when
1.281 ihickson 1083: invoked, it immediately invoked the
1.81 ihickson 1084: method of the same name on the port, with the same arguments, and
1.177 ihickson 1085: returned the same return value.<p>The following are the <span>event handlers</span> (and their
1086: corresponding <span title="event handler event type">event handler
1087: event types</span>) that must be supported, as IDL attributes, by
1088: objects implementing the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
1089: interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1090: <tbody><tr><td><dfn id="handler-dedicatedworkerglobalscope-onmessage" title="handler-DedicatedWorkerGlobalScope-onmessage"><code>onmessage</code></dfn> <td> <code title="event-message">message</code>
1.191 ihickson 1091: </table><p>For the purposes of the <span>application cache</span> networking
1092: model, a dedicated worker is an extension of the <span>cache
1.301 ihickson 1093: host</span> from which it was created.<h4 id="shared-workers-and-the-sharedworkerglobalscope-interface"><span class="secno">4.2.3 </span>Shared workers and the <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> interface</h4><pre class="idl">[Supplemental, NoInterfaceObject]
1.150 ihickson 1094: interface <dfn id="sharedworkerglobalscope">SharedWorkerGlobalScope</dfn> : <a href="#workerglobalscope">WorkerGlobalScope</a> {
1.115 ihickson 1095: readonly attribute DOMString <a href="#dom-sharedworkerglobalscope-name" title="dom-SharedWorkerGlobalScope-name">name</a>;
1.181 ihickson 1096: readonly attribute <span>ApplicationCache</span> <span title="dom-SharedWorkerGlobalScope-applicationCache">applicationCache</span>;
1.308 ! ihickson 1097: [TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-sharedworkerglobalscope-onconnect" title="handler-SharedWorkerGlobalScope-onconnect">onconnect</a>;
1.155 ihickson 1098: };</pre><p>Shared workers receive message ports through <code title="event-WorkerGlobalScope-connect">connect</code> events on
1099: their global object for each connection.<p>The <dfn id="dom-sharedworkerglobalscope-name" title="dom-SharedWorkerGlobalScope-name"><code>name</code></dfn>
1.81 ihickson 1100: attribute must return the value it was assigned when the
1.115 ihickson 1101: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object was created by the
1102: "<a href="#run-a-worker">run a worker</a>" algorithm. Its value represents the name
1.81 ihickson 1103: that can be used to obtain a reference to the worker using the
1.177 ihickson 1104: <code><a href="#sharedworker">SharedWorker</a></code> constructor.<p>The following are the <span>event handlers</span> (and their
1105: corresponding <span title="event handler event type">event handler
1106: event types</span>) that must be supported, as IDL attributes, by
1107: objects implementing the <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1108: interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1109: <tbody><tr><td><dfn id="handler-sharedworkerglobalscope-onconnect" title="handler-SharedWorkerGlobalScope-onconnect"><code>onconnect</code></dfn> <td> <code title="event-connect">connect</code>
1.191 ihickson 1110: </table><p>For the purposes of the <span>application cache</span> networking
1111: model, a shared worker is its own <span>cache host</span>. The
1112: <a href="#run-a-worker">run a worker</a> algorithm takes care of associating the
1113: worker with an <span>application cache</span>.<p class="note">The <code title="dom-SharedWorkerGlobalScope-applicationCache">applicationCache</code>
1.123 ihickson 1114: attribute returns the <code>ApplicationCache</code> object for the
1.301 ihickson 1115: worker.</p><h3 id="origins-of-workers"><span class="secno">4.3 </span>Origins of workers</h3><p>Both the <span>origin</span> and <span>effective script
1.81 ihickson 1116: origin</span> of scripts running in workers are the
1117: <span>origin</span> of the <span>absolute URL</span> given in that
1.115 ihickson 1118: the worker's <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1.301 ihickson 1119: represents.<h3 id="the-event-loop"><span class="secno">4.4 </span>The event loop</h3><p>Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object has an <span>event
1.128 ihickson 1120: loop</span> distinct from those defined for <span title="unit of
1121: related similar-origin browsing contexts">units of related
1122: similar-origin browsing contexts</span>. This <span>event
1123: loop</span> has no associated <span>browsing context</span>, and its
1124: <span title="task queue">task queues</span> only have events,
1125: callbacks, and networking activity as <span title="concept-task">tasks</span>. The processing model of these
1126: <span title="event loop">event loops</span> is defined below in the
1.155 ihickson 1127: <a href="#run-a-worker">run a worker</a> algorithm.<p>Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object also has a <dfn id="dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</dfn> flag, which must
1.81 ihickson 1128: initially be false, but which can get set to true by the algorithms
1.155 ihickson 1129: in the processing model section below.<p>Once the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is set to
1.81 ihickson 1130: true, the <span>event loop</span>'s <span title="task queue">task
1.115 ihickson 1131: queues</span> must discard any further <span title="concept-task">tasks</span> that would be added to them (tasks
1.175 ihickson 1132: already on the queue are unaffected except where otherwise
1.115 ihickson 1133: specified). Effectively, once the <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is true,
1.81 ihickson 1134: timers stop firing, notifications for all pending asynchronous
1.301 ihickson 1135: operations are dropped, etc.<h3 id="the-worker-s-lifetime"><span class="secno">4.5 </span>The worker's lifetime</h3><p>Workers communicate with other workers and with <span title="browsing context">browsing contexts</span> through <span title="channel messaging">message channels</span> and their
1136: <code><a href="#messageport">MessagePort</a></code> objects.<p>Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> <var title="">worker global
1.124 ihickson 1137: scope</var> has a list of <dfn id="the-worker-s-ports">the worker's ports</dfn>, which
1.301 ihickson 1138: consists of all the <code><a href="#messageport">MessagePort</a></code> objects that are
1.81 ihickson 1139: entangled with another port and that have one (but only one) port
1140: owned by <var title="">worker global scope</var>. This list includes
1.281 ihickson 1141: the implicit
1.301 ihickson 1142: <code><a href="#messageport">MessagePort</a></code> in the case of <a href="#dedicatedworkerglobalscope" title="DedicatedWorkerGlobalScope">dedicated workers</a>.<p>Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> also has a list of <dfn id="the-worker-s-workers">the
1.124 ihickson 1143: worker's workers</dfn>. Initially this list is empty; it is
1.155 ihickson 1144: populated when the worker creates or obtains further workers.<p>Finally, each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> also has a list of
1.124 ihickson 1145: <dfn id="the-worker-s-documents">the worker's <code>Document</code>s</dfn>. Initially this list
1.155 ihickson 1146: is empty; it is populated when the worker is created.<p>Whenever a <code>Document</code> <var title="">d</var> is <dfn id="add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">added to the
1.123 ihickson 1147: worker's <code>Document</code>s</dfn>, the user agent must, for each
1.124 ihickson 1148: worker in the list of <a href="#the-worker-s-workers">the worker's workers</a> whose list
1149: of <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a> does not contain
1150: <var title="">d</var>, <a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's
1.123 ihickson 1151: documents">add <var title="">d</var> to <var title="">q</var>'s
1152: <code>WorkerGlobalScope</code> owner's list of <span>the worker's
1.281 ihickson 1153: <code>Document</code>s</span></a>.</p><p>Whenever a <code>Document</code> object is <span title="discard a
1.123 ihickson 1154: Document">discarded</span>, it must be removed from the list of
1155: <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a> of each worker
1.192 ihickson 1156: whose list contains that <code>Document</code>.<p>Given a <span>script's global object</span> <var title="">o</var>
1.123 ihickson 1157: when creating or obtaining a worker, the <dfn id="list-of-relevant-document-objects-to-add">list of relevant
1158: <code>Document</code> objects to add</dfn> depends on the type of
1159: <var title="">o</var>. If <var title="">o</var> is a
1160: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object (i.e. if we are creating a
1161: nested worker), then the relevant <code>Document</code>s are the
1162: <code>Document</code>s that are in <var title="">o</var>'s own list
1163: of <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a>. Otherwise, <var title="">o</var> is a <code>Window</code> object, and the relevant
1164: <code>Document</code> is just the <code>Document</code> that is the
1.155 ihickson 1165: <span>active document</span> of the <code>Window</code> object <var title="">o</var>.<hr><p>A worker is said to be a <dfn id="permissible-worker">permissible worker</dfn> if its
1.123 ihickson 1166: list of <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a> is not
1.155 ihickson 1167: empty.<p>A worker is said to be a <dfn id="protected-worker">protected worker</dfn> if it is a
1.123 ihickson 1168: <a href="#permissible-worker">permissible worker</a> and either it has outstanding
1169: timers, database transactions, or network connections, or its list
1.124 ihickson 1170: of <a href="#the-worker-s-ports">the worker's ports</a> is not empty, or its
1.123 ihickson 1171: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> is actually a
1172: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object (i.e. the worker is a
1.155 ihickson 1173: shared worker).<p>A worker is said to be an <dfn id="active-needed-worker">active needed worker</dfn> if any
1.123 ihickson 1174: of the <code>Document</code> objects in <a href="#the-worker-s-documents">the worker's
1.155 ihickson 1175: <code>Document</code>s</a> are <span>fully active</span>.<p>A worker is said to be a <dfn id="suspendable-worker">suspendable worker</dfn> if it is
1.123 ihickson 1176: not an <a href="#active-needed-worker">active needed worker</a> but it is a
1.301 ihickson 1177: <a href="#permissible-worker">permissible worker</a>.<h3 id="processing-model"><span class="secno">4.6 </span>Processing model</h3><p>When a user agent is to <dfn id="run-a-worker">run a worker</dfn> for a script with
1.232 ihickson 1178: <span>URL</span> <var title="">url</var>, a <span>browsing
1179: context</span> <var title="">owner browsing context</var>, a
1180: <code>Document</code> <var title="">owner document</var>, an
1181: <span>origin</span> <var title="">owner origin</var>, and with
1182: global scope <var title="">worker global scope</var>, it must run
1183: the following steps:<ol><li>
1.81 ihickson 1184:
1.274 ihickson 1185: <p>Create a separate parallel execution environment (i.e. a
1186: separate thread or process or equivalent construct), and run the
1187: rest of these steps asynchronously in that context.</p>
1.81 ihickson 1188:
1189: </li>
1.4 ihickson 1190:
1.101 ihickson 1191: <li><p>If <var title="">worker global scope</var> is actually a
1.115 ihickson 1192: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object (i.e. the worker is a
1.101 ihickson 1193: shared worker), and there are any <span title="relevant application
1194: cache">relevant application caches</span> that are identified by a
1195: manifest URL with the <span>same origin</span> as <var title="">url</var> and that have <var title="">url</var> as one of
1.115 ihickson 1196: their entries, <em>not</em> excluding entries marked as <span title="concept-appcache-foreign">foreign</span>, then associate the
1197: <var title="">worker global scope</var> with the <span title="concept-appcache-selection">most appropriate application
1.101 ihickson 1198: cache</span> of those that match.</li>
1199:
1.4 ihickson 1200: <li>
1.52 ihickson 1201:
1.256 ihickson 1202: <p>Attempt to <span>fetch</span> the resource identified by <var title="">url</var>, from the <var title="">owner origin</var>,
1203: with the <i>synchronous flag</i> set and the <i>force same-origin
1.281 ihickson 1204: flag</i> set.</p>
1.256 ihickson 1205: <p>If the attempt fails, then for each <code><a href="#worker">Worker</a></code> or
1206: <code><a href="#sharedworker">SharedWorker</a></code> object associated with <var title="">worker global scope</var>, <span>queue a task</span> to
1207: <span>fire a simple event</span> named <code title="event-error">error</code> at that object. Abort these
1208: steps.</p>
1.7 ihickson 1209:
1.264 ihickson 1210: <p>If the attempt succeeds, then let <var title="">source</var> be
1211: the script resource <span>decoded as UTF-8, with error
1212: handling</span>.
1213:
1214: <a href="#refsHTML">[HTML]</a>
1215:
1216: </p>
1.81 ihickson 1217:
1.68 ihickson 1218: <p>Let <var title="">language</var> be JavaScript.</p>
1.7 ihickson 1219:
1.115 ihickson 1220: <p class="note">As with <code>script</code> elements, the MIME
1.81 ihickson 1221: type of the script is ignored. Unlike with <code>script</code>
1222: elements, there is no way to override the type. It's always
1.170 ihickson 1223: assumed to be JavaScript.</p>
1.81 ihickson 1224:
1225: </li>
1.7 ihickson 1226:
1227: <li>
1.68 ihickson 1228:
1.115 ihickson 1229: <p>A new <span title="concept-script">script</span> is now
1.81 ihickson 1230: created, as follows.</p>
1231:
1232: <p>Create a new <span>script execution environment</span>
1233: set up as appropriate for the scripting language <var title="">language</var>.</p>
1.34 ihickson 1234:
1.68 ihickson 1235: <p>Parse/compile/initialize <var title="">source</var> using that
1.81 ihickson 1236: <span>script execution environment</span>, as appropriate for <var title="">language</var>, and thus obtain a <span>list of code
1237: entry-points</span>; set the <i>initial code entry-point</i> to
1238: the entry-point for any executable code to be immediately run.</p>
1239:
1240: <p>Set the <span>script's global object</span> to <var title="">worker global scope</var>.</p>
1241:
1242: <p>Set the <span>script's browsing context</span> to <var title="">owner browsing context</var>.</p>
1243:
1.232 ihickson 1244: <p>Set the <span>script's document</span> to <var title="">owner
1245: document</var>.</p>
1246:
1.83 ihickson 1247: <p>Set the <span>script's URL character encoding</span> to
1.81 ihickson 1248: UTF-8. (This is just used for encoding non-ASCII characters in the
1249: query component of URLs.)</p>
1.68 ihickson 1250:
1251: <p>Set the <span>script's base URL</span> to <var title="">url</var>.</p>
1.4 ihickson 1252:
1.81 ihickson 1253: </li>
1.4 ihickson 1254:
1255: <li>
1.81 ihickson 1256:
1257: <p><strong>Closing orphan workers</strong>: Start monitoring the
1.125 ihickson 1258: worker such that no sooner than it stops being either a
1259: <a href="#protected-worker">protected worker</a> or a <a href="#suspendable-worker">suspendable
1.123 ihickson 1260: worker</a>, and no later than it stops being a
1261: <a href="#permissible-worker">permissible worker</a>, <var title="">worker global
1262: scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is set
1.281 ihickson 1263: to true.</p>
1.81 ihickson 1264:
1265: </li>
1.9 ihickson 1266:
1267: <li>
1.7 ihickson 1268:
1.81 ihickson 1269: <p><strong>Suspending workers</strong>: Start monitoring the
1270: worker, such that whenever <var title="">worker global
1.115 ihickson 1271: scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is false
1272: and the worker is a <a href="#suspendable-worker">suspendable worker</a>, the user
1.81 ihickson 1273: agent suspends execution of script in that worker until such time
1.115 ihickson 1274: as either the <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag switches
1275: to true or the worker stops being a <a href="#suspendable-worker">suspendable
1.81 ihickson 1276: worker</a>.</p>
1.4 ihickson 1277:
1.81 ihickson 1278: </li>
1.68 ihickson 1279:
1280: <li>
1.4 ihickson 1281:
1.81 ihickson 1282: <p><span title="jump to a code entry-point">Jump</span> to the
1.115 ihickson 1283: <span title="concept-script">script</span>'s <i>initial code
1.81 ihickson 1284: entry-point</i>, and let that run until it either returns, fails
1285: to catch an exception, or gets prematurely aborted by the
1.115 ihickson 1286: "<a href="#kill-a-worker">kill a worker</a>" or "<a href="#terminate-a-worker">terminate a worker</a>"
1.81 ihickson 1287: algorithms defined below.</p>
1288:
1.4 ihickson 1289:
1.81 ihickson 1290: </li>
1.4 ihickson 1291:
1.95 ihickson 1292: <li><p>If <var title="">worker global scope</var> is actually a
1.115 ihickson 1293: <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object (i.e. the worker is
1.126 ihickson 1294: a dedicated worker), then enable the <span>port message
1295: queue</span> of the worker's implicit port.</li>
1.95 ihickson 1296:
1.4 ihickson 1297: <li>
1.68 ihickson 1298:
1.115 ihickson 1299: <p><i title="">Event loop</i>: Wait until either there is a <span title="concept-task">task</span> in one of the <span>event
1300: loop</span>'s <span title="task queue">task queues</span> or <var title="">worker global scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is set
1.81 ihickson 1301: to true.</p>
1.43 ihickson 1302:
1.81 ihickson 1303: </li>
1.4 ihickson 1304:
1305: <li>
1306:
1.81 ihickson 1307: <p>Run the oldest task on one of the <span>event loop</span>'s
1308: <span title="task queue">task queues</span>, if any. The user
1309: agent may pick any <span>task queue</span>.</p>
1310:
1.115 ihickson 1311: <p class="note">The handling of events or the execution of
1312: callbacks might get prematurely aborted by the "<a href="#kill-a-worker">kill a
1313: worker</a>" or "<a href="#terminate-a-worker">terminate a worker</a>" algorithms
1.81 ihickson 1314: defined below.</p>
1.8 ihickson 1315:
1.81 ihickson 1316: </li>
1.4 ihickson 1317:
1318: <li>
1319:
1.248 ihickson 1320: <p>If the <span>storage mutex</span> is now owned by the worker's
1321: <span>event loop</span>, release it so that it is once again
1322: free.</p>
1323:
1324: </li>
1325:
1326: <li>
1327:
1328: <p>Remove the task just run in the earlier step, if any, from its
1.81 ihickson 1329: <span>task queue</span>.</p>
1.4 ihickson 1330:
1.81 ihickson 1331: </li>
1.4 ihickson 1332:
1333: <li>
1.8 ihickson 1334:
1.81 ihickson 1335: <p>If there are any more events in the <span>event loop</span>'s
1.115 ihickson 1336: <span title="task queue">task queues</span> or if <var title="">worker global scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is set
1.81 ihickson 1337: to false, then jump back to the step above labeled <i>event
1338: loop</i>.</p>
1.8 ihickson 1339:
1.81 ihickson 1340: </li>
1.8 ihickson 1341:
1342: <li>
1.71 ihickson 1343:
1.123 ihickson 1344: <p>Empty the <var title="">worker global scope</var>'s <span>list
1345: of active timeouts</span> and its <span>list of active
1346: intervals</span>.</p>
1.50 ihickson 1347:
1.81 ihickson 1348: </li>
1.50 ihickson 1349:
1.247 ihickson 1350: <li>
1351:
1352: <p>Disentangle all the ports in the list of <a href="#the-worker-s-ports">the worker's
1353: ports</a>.</p>
1354:
1355: </li>
1356:
1.155 ihickson 1357: </ol><hr><p>When a user agent is to <dfn id="kill-a-worker">kill a worker</dfn> it must
1.81 ihickson 1358: run the following steps in parallel with the worker's main loop (the
1.281 ihickson 1359: "<a href="#run-a-worker">run a worker</a>" processing model defined above):<ol><li><p>Set the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag to
1.81 ihickson 1360: true.</li>
1361:
1362:
1.115 ihickson 1363: <li><p>If there are any <span title="concept-task">tasks</span>
1.81 ihickson 1364: queued in the <span>event loop</span>'s <span title="task
1.281 ihickson 1365: queue">task queues</span>, discard them without processing them.</li>
1366:
1.81 ihickson 1367:
1368: <li><p>Wait a user-agent-defined amount of time.</li>
1369:
1.281 ihickson 1370: <li><p>Abort the script currently running in the worker.</li>
1.81 ihickson 1371:
1.155 ihickson 1372: </ol><p>User agents may invoke the "<a href="#kill-a-worker">kill a worker</a>"
1.81 ihickson 1373: processing model on a worker at any time, e.g. in response to user
1374: requests, in response to CPU quota management, or when a worker
1.115 ihickson 1375: stops being an <a href="#active-needed-worker">active needed worker</a> if the worker
1376: continues executing even after its <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag was
1.155 ihickson 1377: set to true.<hr><p>When a user agent is to <dfn id="terminate-a-worker">terminate a worker</dfn> it must run
1.81 ihickson 1378: the following steps in parallel with the worker's main loop (the
1.155 ihickson 1379: "<a href="#run-a-worker">run a worker</a>" processing model defined above):<ol><li><p>Set the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's
1.115 ihickson 1380: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag to
1.81 ihickson 1381: true.</li>
1382:
1.115 ihickson 1383: <li><p>If there are any <span title="concept-task">tasks</span>
1.81 ihickson 1384: queued in the <span>event loop</span>'s <span title="task
1385: queue">task queues</span>, discard them without processing
1386: them.</li>
1387:
1388: <li><p>Abort the script currently running in the worker.</li>
1389:
1.115 ihickson 1390: <li><p>If the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object is
1391: actually a <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object (i.e. the
1.81 ihickson 1392: worker is a dedicated worker), then empty the <span>port message
1393: queue</span> of the port that the worker's implicit port is
1394: entangled with.</li>
1395:
1.155 ihickson 1396: </ol><hr><p>The <span>task source</span> for the tasks mentioned above is the
1.301 ihickson 1397: <span>DOM manipulation task source</span>.<h3 id="runtime-script-errors"><span class="secno">4.7 </span>Runtime script errors</h3><p>Whenever an uncaught runtime script error occurs in one of the
1.143 ihickson 1398: worker's scripts, if the error did not occur while handling a
1399: previous script error, the user agent must <span>report the
1400: error</span> using the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's <code title="handler-WorkerGlobalScope-onerror"><a href="#handler-workerglobalscope-onerror">onerror</a></code>
1.205 ihickson 1401: attribute.
1402:
1.226 ihickson 1403: <a href="#refsHTML">[HTML]</a>
1.205 ihickson 1404:
1405: <p>For shared workers, if the error is still <i title="concept-error-nothandled">not handled</i> afterwards, or if
1.132 ihickson 1406: the error occurred while handling a previous script error, the error
1.215 ihickson 1407: may be reported to the user.
1.205 ihickson 1408:
1.226 ihickson 1409: <a href="#refsHTML">[HTML]</a>
1.205 ihickson 1410:
1411: <p>For dedicated workers, if the error is still <i title="concept-error-nothandled">not handled</i> afterwards, or if
1.132 ihickson 1412: the error occurred while handling a previous script error, the user
1.292 ihickson 1413: agent must <span>queue a task</span> to fire an event that uses the
1414: <code><a href="#errorevent">ErrorEvent</a></code> interface, with the name <code title="event-error">error</code>, that doesn't bubble and is
1.307 ihickson 1415: cancelable, with its <code title="dom-ErrorEvent-message"><a href="#dom-errorevent-message">message</a></code>, <code title="dom-ErrorEvent-filename"><a href="#dom-errorevent-filename">filename</a></code>, and <code title="dom-ErrorEvent-lineno"><a href="#dom-errorevent-lineno">lineno</a></code> attributes initialized
1.292 ihickson 1416: appropriately, at the <code><a href="#worker">Worker</a></code> object associated with the
1.307 ihickson 1417: worker. If the event is not canceled, the user agent must act as if
1418: the uncaught runtime script error had occurred in the global scope
1419: that the <code><a href="#worker">Worker</a></code> object is in, thus repeating the entire
1.292 ihickson 1420: runtime script error reporting process one level up.<p>If the implicit port connecting the worker to its
1421: <code><a href="#worker">Worker</a></code> object has been disentangled (i.e. if the parent
1422: worker has been terminated), then the user agent must act as if the
1423: <code><a href="#worker">Worker</a></code> object had no <code title="event-error">error</code> event handler and as if that
1424: worker's <code title="handler-WorkerGlobalScope-onerror"><a href="#handler-workerglobalscope-onerror">onerror</a></code> attribute
1425: was null, but must otherwise act as described above.<p class="note">Thus, error reports proagate up to the chain of
1426: dedicated workers up to the original <code>Document</code>, even if
1427: some of the workers along this chain have been terminated and
1428: garbage collected.<p>The <span>task source</span> for the task mentioned above is the
1.307 ihickson 1429: <span>DOM manipulation task source</span>.<hr><pre class="idl">[Constructor(DOMString type, optional <a href="#erroreventinit">ErrorEventInit</a> eventInitDict)]
1430: interface <dfn id="errorevent">ErrorEvent</dfn> : <span>Event</span> {
1.147 ihickson 1431: readonly attribute DOMString <a href="#dom-errorevent-message" title="dom-ErrorEvent-message">message</a>;
1432: readonly attribute DOMString <a href="#dom-errorevent-filename" title="dom-ErrorEvent-filename">filename</a>;
1.115 ihickson 1433: readonly attribute unsigned long <a href="#dom-errorevent-lineno" title="dom-ErrorEvent-lineno">lineno</a>;
1.307 ihickson 1434: };
1435:
1436: dictionary <dfn id="erroreventinit">ErrorEventInit</dfn> : <span>EventInit</span> {
1437: DOMString message;
1438: DOMString filename;
1439: unsigned long lineno;
1440: };</pre><p>The <dfn id="dom-errorevent-message" title="dom-ErrorEvent-message"><code>message</code></dfn> attribute
1441: must return the value it was initialized to. When the object is
1442: created, this attribute must be initialized to the empty string. It
1443: represents the error message.<p>The <dfn id="dom-errorevent-filename" title="dom-ErrorEvent-filename"><code>filename</code></dfn>
1444: attribute must return the value it was initialized to. When the
1445: object is created, this attribute must be initialized to the empty
1446: string. It represents the <span>absolute URL</span> of the script in
1.155 ihickson 1447: which the error originally occurred.<p>The <dfn id="dom-errorevent-lineno" title="dom-ErrorEvent-lineno"><code>lineno</code></dfn>
1.307 ihickson 1448: attribute must return the value it was initialized to. When the
1449: object is created, this attribute must be initialized to zero. It
1450: represents the line number where the error occurred in the
1.301 ihickson 1451: script.<h3 id="creating-workers"><span class="secno">4.8 </span>Creating workers</h3><h4 id="the-abstractworker-abstract-interface"><span class="secno">4.8.1 </span>The <code><a href="#abstractworker">AbstractWorker</a></code> abstract interface</h4><pre class="idl">[Supplemental, NoInterfaceObject]
1.302 ihickson 1452: interface <dfn id="abstractworker">AbstractWorker</dfn> : <span>EventTarget</span> {
1.308 ! ihickson 1453: [TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-abstractworker-onerror" title="handler-AbstractWorker-onerror">onerror</a>;
1.302 ihickson 1454: };</pre><p>The following are the <span>event handlers</span> (and their
1.177 ihickson 1455: corresponding <span title="event handler event type">event handler
1456: event types</span>) that must be supported, as IDL attributes, by
1457: objects implementing the <code><a href="#abstractworker">AbstractWorker</a></code> interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1458: <tbody><tr><td><dfn id="handler-abstractworker-onerror" title="handler-AbstractWorker-onerror"><code>onerror</code></dfn> <td> <code title="event-error">error</code>
1.306 ihickson 1459: </table><h4 id="dedicated-workers-and-the-worker-interface"><span class="secno">4.8.2 </span>Dedicated workers and the <code><a href="#worker">Worker</a></code> interface</h4><pre class="idl">[<a href="#dom-worker" title="dom-Worker">Constructor</a>(DOMString scriptURL)]
1.115 ihickson 1460: interface <dfn id="worker">Worker</dfn> : <a href="#abstractworker">AbstractWorker</a> {
1461: void <a href="#dom-worker-terminate" title="dom-Worker-terminate">terminate</a>();
1.50 ihickson 1462:
1.308 ! ihickson 1463: void <a href="#dom-worker-postmessage" title="dom-Worker-postMessage">postMessage</a>(any message, optional sequence<<span>Transferable</span>> transfer); [TreatNonCallableAsNull] attribute <span>Function</span>? <a href="#handler-worker-onmessage" title="handler-Worker-onmessage">onmessage</a>;
1.155 ihickson 1464: };</pre><p>The <dfn id="dom-worker-terminate" title="dom-Worker-terminate"><code>terminate()</code></dfn> method,
1.115 ihickson 1465: when invoked, must cause the "<a href="#terminate-a-worker">terminate a worker</a>"
1.81 ihickson 1466: algorithm to be run on the worker with with the object is
1.155 ihickson 1467: associated.<p><code><a href="#worker">Worker</a></code> objects act as if they had an implicit
1.301 ihickson 1468: <code><a href="#messageport">MessagePort</a></code> associated with them. This port is part of
1.81 ihickson 1469: a channel that is set up when the worker is created, but it is not
1470: exposed. This object must never be garbage collected before the
1.155 ihickson 1471: <code><a href="#worker">Worker</a></code> object.<p>All messages received by that port must immediately be retargeted
1.281 ihickson 1472: at the <code><a href="#worker">Worker</a></code> object.<p>The <dfn id="dom-worker-postmessage" title="dom-Worker-postMessage"><code>postMessage()</code></dfn> method on <code><a href="#worker">Worker</a></code> objects
1473: must act as if, when invoked, it
1.81 ihickson 1474: immediately invoked the method of the same name on the port, with
1.177 ihickson 1475: the same arguments, and returned the same return value.<p>The following are the <span>event handlers</span> (and their
1476: corresponding <span title="event handler event type">event handler
1477: event types</span>) that must be supported, as IDL attributes, by
1478: objects implementing the <code><a href="#worker">Worker</a></code> interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1479: <tbody><tr><td><dfn id="handler-worker-onmessage" title="handler-Worker-onmessage"><code>onmessage</code></dfn> <td> <code title="event-message">message</code>
1480: </table><hr><p>When the <dfn id="dom-worker" title="dom-Worker"><code>Worker(<var title="">scriptURL</var>)</code></dfn> constructor is invoked, the
1.216 ihickson 1481: user agent must run the following steps:<ol><li><p><span title="resolve a url">Resolve</span> the <var title="">scriptURL</var> argument relative to the <span>entry
1.133 ihickson 1482: script</span>'s <span title="script's base URL">base URL</span>,
1483: when the method is invoked.</li>
1.9 ihickson 1484:
1.81 ihickson 1485: <li><p>If this fails, throw a <code>SYNTAX_ERR</code>
1486: exception.</li>
1.9 ihickson 1487:
1.167 ihickson 1488: <li>
1489:
1490: <p>If the <span>origin</span> of the resulting <span>absolute
1491: URL</span> is not the <span title="same origin">same</span> as the
1.216 ihickson 1492: origin of the <span>entry script</span>, then throw a
1.182 ihickson 1493: <code>SECURITY_ERR</code> exception.</p>
1.167 ihickson 1494:
1495: <p class="note">Thus, scripts must be external files with the same
1.269 ihickson 1496: scheme as the original page: you can't load a script from a <span title="data protocol"><code title="">data:</code> URL</span> or
1497: <span title="javascript protocol"><code title="">javascript:</code> URL</span>, and an <code>http:</code>
1498: page couldn't start workers using scripts with <code>http:</code>
1499: URLs.</p>
1.167 ihickson 1500:
1501: </li>
1.9 ihickson 1502:
1.185 ihickson 1503: <li><p>Create a new <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
1504: object. Let <var title="">worker global scope</var> be this new
1505: object.</li>
1.9 ihickson 1506:
1.115 ihickson 1507: <li><p>Create a new <code><a href="#worker">Worker</a></code> object, associated with
1.81 ihickson 1508: <var title="">worker global scope</var>. Let <var title="">worker</var> be this new object.</li>
1.50 ihickson 1509:
1.301 ihickson 1510: <li><p><span>Create a new <code><a href="#messageport">MessagePort</a></code> object</span>
1.192 ihickson 1511: owned by the <span title="script's global object">global
1512: object</span> of the <span title="concept-script">script</span> that
1.185 ihickson 1513: invoked the constructor. Let this be the <var title="">outside
1.81 ihickson 1514: port</var>.</li>
1.9 ihickson 1515:
1.81 ihickson 1516: <li><p>Associate the <var title="">outside port</var> with <var title="">worker</var>.</li>
1.50 ihickson 1517:
1.301 ihickson 1518: <li><p><span>Create a new <code><a href="#messageport">MessagePort</a></code> object</span>
1.185 ihickson 1519: owned by <var title="">worker global scope</var>. Let <var title="">inside port</var> be this new object.</li>
1.50 ihickson 1520:
1.81 ihickson 1521: <li><p>Associate <var title="">inside port</var> with <var title="">worker global scope</var>.</li>
1.50 ihickson 1522:
1.81 ihickson 1523: <li><p><span>Entangle</span> <var title="">outside port</var> and
1524: <var title="">inside port</var>.</li>
1.50 ihickson 1525:
1.81 ihickson 1526: <li><p>Return <var title="">worker</var>, and run the following
1527: steps asynchronously.</li>
1.50 ihickson 1528:
1529:
1.126 ihickson 1530: <li><p>Enable <var title="">outside port</var>'s <span>port message
1.81 ihickson 1531: queue</span>.</li>
1.50 ihickson 1532:
1533: <li>
1.51 ihickson 1534:
1.123 ihickson 1535: <p>Let <var title="">docs</var> be the <a href="#list-of-relevant-document-objects-to-add">list of relevant
1.192 ihickson 1536: <code>Document</code> objects to add</a> given the <span title="script's global object">global object</span> of the <span title="concept-script">script</span> that invoked the
1.123 ihickson 1537: constructor.</p>
1538:
1539: </li>
1540:
1541: <li>
1542:
1543: <p><a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">Add to
1544: <var title="">worker global scope</var>'s list of <span>the
1545: worker's <code>Document</code>s</span></a> the
1546: <code>Document</code> objects in <var title="">docs</var>.</p>
1547:
1548: </li>
1549:
1550: <li>
1551:
1.192 ihickson 1552: <p>If the <span title="script's global object">global object</span>
1.124 ihickson 1553: of the <span title="concept-script">script</span> that invoked the
1554: constructor is a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object (i.e. we
1555: are creating a nested worker), add <var title="">worker global
1556: scope</var> to the list of <a href="#the-worker-s-workers">the worker's workers</a> of the
1.192 ihickson 1557: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object that is the <span title="script's global object">global object</span> of the <span title="concept-script">script</span> that invoked the
1.124 ihickson 1558: constructor.</p>
1559:
1560: </li>
1561:
1562: <li>
1563:
1.115 ihickson 1564: <p><a href="#run-a-worker">Run a worker</a> for the resulting <span>absolute
1.193 ihickson 1565: URL</span>, with the <span>script's browsing context</span> of the
1.81 ihickson 1566: script that invoked the method as the <var title="">owner browsing
1.232 ihickson 1567: context</var>, with the <span>script's document</span> of the
1568: script that invoked the method as the <var title="">owner
1569: document</var>, with the <span>origin</span> of the <span>entry
1.176 ihickson 1570: script</span> as the <var title="">owner origin</var>, and with
1571: <var title="">worker global scope</var> as the global scope.</p>
1.9 ihickson 1572:
1.81 ihickson 1573: </li>
1.4 ihickson 1574:
1.155 ihickson 1575: </ol><p>This constructor must be visible when the <span>script's global
1.192 ihickson 1576: object</span> is either a <code>Window</code> object or an object
1.306 ihickson 1577: implementing the <code><a href="#workerutils">WorkerUtils</a></code> interface.<h4 id="shared-workers-and-the-sharedworker-interface"><span class="secno">4.8.3 </span>Shared workers and the <code><a href="#sharedworker">SharedWorker</a></code> interface</h4><pre class="idl">[<a href="#dom-sharedworker" title="dom-SharedWorker">Constructor</a>(DOMString scriptURL, optional DOMString name)]
1.115 ihickson 1578: interface <dfn id="sharedworker">SharedWorker</dfn> : <a href="#abstractworker">AbstractWorker</a> {
1.301 ihickson 1579: readonly attribute <a href="#messageport">MessagePort</a> <a href="#dom-sharedworker-port" title="dom-SharedWorker-port">port</a>;
1.155 ihickson 1580: };</pre><p>The <dfn id="dom-sharedworker-port" title="dom-SharedWorker-port"><code>port</code></dfn>
1.81 ihickson 1581: attribute must return the value it was assigned by the object's
1.301 ihickson 1582: constructor. It represents the <code><a href="#messageport">MessagePort</a></code> for
1.155 ihickson 1583: communicating with the shared worker.<p>When the <dfn id="dom-sharedworker" title="dom-SharedWorker"><code>SharedWorker(<var title="">scriptURL</var>, <var title="">name</var>)</code></dfn>
1.81 ihickson 1584: constructor is invoked, the user agent must run the following
1.155 ihickson 1585: steps:<ol><li><p><span title="resolve a url">Resolve</span> the <var title="">scriptURL</var> argument.</li>
1.81 ihickson 1586:
1587: <li><p>If this fails, throw a <code>SYNTAX_ERR</code>
1588: exception.</li>
1589:
1.159 ihickson 1590: <li><p>Otherwise, let <var title="">scriptURL</var> be the
1591: resulting <span>absolute URL</span>.</li>
1592:
1593: <li><p>Let <var title="">name</var> be the value of the second
1.164 ihickson 1594: argument, or the empty string if the second argument was
1595: omitted.</li>
1.159 ihickson 1596:
1.167 ihickson 1597: <li>
1598:
1599: <p>If the <span>origin</span> of <var title="">scriptURL</var> is
1600: not the <span title="same origin">same</span> as the origin of the
1.216 ihickson 1601: <span>entry script</span>, then throw a <code>SECURITY_ERR</code>
1.182 ihickson 1602: exception.</p>
1.167 ihickson 1603:
1604: <p class="note">Thus, scripts must be external files with the same
1.269 ihickson 1605: scheme as the original page: you can't load a script from a <span title="data protocol"><code title="">data:</code> URL</span> or
1606: <span title="javascript protocol"><code title="">javascript:</code> URL</span>, and a <code>http:</code>
1607: page couldn't start workers using scripts with <code>http:</code>
1608: URLs.</p>
1.167 ihickson 1609:
1610: </li>
1.9 ihickson 1611:
1612: <li>
1613:
1.123 ihickson 1614: <p>Let <var title="">docs</var> be the <a href="#list-of-relevant-document-objects-to-add">list of relevant
1.192 ihickson 1615: <code>Document</code> objects to add</a> given the <span title="script's global object">global object</span> of the <span title="concept-script">script</span> that invoked the
1.123 ihickson 1616: constructor.</p>
1617:
1618: </li>
1619:
1620: <li>
1621:
1.50 ihickson 1622: <p>Execute the following substeps atomically:</p>
1.9 ihickson 1623:
1.155 ihickson 1624: <ol><li><p>Create a new <code><a href="#sharedworker">SharedWorker</a></code> object, which will
1.115 ihickson 1625: shortly be associated with a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1626: object. Let this <code><a href="#sharedworker">SharedWorker</a></code> object be <var title="">worker</var>.</li>
1.81 ihickson 1627:
1.301 ihickson 1628: <li><p><span>Create a new <code><a href="#messageport">MessagePort</a></code> object</span>
1.192 ihickson 1629: owned by the <span title="script's global object">global
1630: object</span> of the script that invoked the method. Let this be
1.123 ihickson 1631: the <var title="">outside port</var>.</li>
1.81 ihickson 1632:
1.115 ihickson 1633: <li><p>Assign <var title="">outside port</var> to the <code title="dom-SharedWorker-port"><a href="#dom-sharedworker-port">port</a></code> attribute of <var title="">worker</var>.</li>
1.81 ihickson 1634:
1.164 ihickson 1635: <li><p>Let <var title="">worker global scope</var> be
1636: null.</li>
1637:
1638: <li><p>If <var title="">name</var> is not the empty string and
1639: there exists a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object whose
1640: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag
1641: is false, whose <code title="dom-WorkerGlobalScope-name">name</code> attribute is
1642: exactly equal to <var title="">name</var>, and whose <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1643: represents an <span>absolute URL</span> with the <span>same
1644: origin</span> as <var title="">scriptURL</var>, then let <var title="">worker global scope</var> be that
1645: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object.</li>
1646:
1647: <li><p>Otherwise, if <var title="">name</var> is the empty string
1648: and there exists a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object
1649: whose <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a>
1.293 ihickson 1650: flag is false, whose <code title="dom-WorkerGlobalScope-name">name</code> attribute is the
1651: empty string, and whose <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1.237 ihickson 1652: represents an <span>absolute URL</span> that is exactly equal to
1653: <var title="">scriptURL</var>, then let <var title="">worker
1654: global scope</var> be that <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1655: object.</li>
1.164 ihickson 1656:
1.9 ihickson 1657: <li>
1658:
1.164 ihickson 1659: <p>If <var title="">worker global scope</var> is not null, then
1660: run these steps:</p>
1.81 ihickson 1661:
1.164 ihickson 1662: <ol><li><p>If <var title="">worker global scope</var>'s <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code>
1.81 ihickson 1663: attribute represents an <span>absolute URL</span> that is not
1.159 ihickson 1664: exactly equal to <var title="">scriptURL</var>, then throw a
1665: <code>URL_MISMATCH_ERR</code> exception and abort all these
1666: steps.</li>
1.81 ihickson 1667:
1668: <li><p>Associate <var title="">worker</var> with <var title="">worker global scope</var>.</li>
1669:
1.301 ihickson 1670: <li><p><span>Create a new <code><a href="#messageport">MessagePort</a></code>
1.185 ihickson 1671: object</span> owned by <var title="">worker global
1672: scope</var>. Let this be the <var title="">inside
1673: port</var>.</li>
1.81 ihickson 1674:
1675: <li><p><span>Entangle</span> <var title="">outside port</var>
1676: and <var title="">inside port</var>.</li>
1677:
1678: <li><p>Return <var title="">worker</var> and perform the next
1679: step asynchronously.</li>
1.9 ihickson 1680:
1.81 ihickson 1681: <li><p>Create an event that uses the <code>MessageEvent</code>
1.115 ihickson 1682: interface, with the name <code title="event-connect">connect</code>, which does not bubble, is
1.118 ihickson 1683: not cancelable, has no default action, has a <code title="dom-MessageEvent-data">data</code> attribute whose value
1.307 ihickson 1684: is initialized to the empty string and has a <code title="dom-MessageEvent-ports">ports</code> attribute whose
1685: value is initialized to a <span title="dfn-read-only-array">read only</span> array containing
1686: only the newly created port, and <span>queue a task</span> to
1687: dispatch the event at <var title="">worker global
1688: scope</var>.</li>
1.43 ihickson 1689:
1.123 ihickson 1690: <li>
1691:
1692: <p><a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">Add to
1693: <var title="">worker global scope</var>'s list of <span>the
1694: worker's <code>Document</code>s</span></a> the
1695: <code>Document</code> objects in <var title="">docs</var>.</p>
1696:
1697: </li>
1698:
1.124 ihickson 1699: <li>
1700:
1.192 ihickson 1701: <p>If the <span title="script's global object">global
1702: object</span> of the <span title="concept-script">script</span>
1.124 ihickson 1703: that invoked the constructor is a
1704: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, add <var title="">worker global scope</var> to the list of <a href="#the-worker-s-workers">the
1705: worker's workers</a> of the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1.192 ihickson 1706: object that is the <span title="script's global object">global
1707: object</span> of the <span title="concept-script">script</span>
1.124 ihickson 1708: that invoked the constructor.</p>
1709:
1710: </li>
1711:
1.81 ihickson 1712: <li><p>Abort all these steps.</li>
1.9 ihickson 1713:
1.155 ihickson 1714: </ol></li>
1.9 ihickson 1715:
1.185 ihickson 1716: <li><p>Create a new <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1717: object. Let <var title="">worker global scope</var> be this new
1718: object.</li>
1.9 ihickson 1719:
1.81 ihickson 1720: <li><p>Associate <var title="">worker</var> with <var title="">worker global scope</var>.</li>
1.9 ihickson 1721:
1.115 ihickson 1722: <li><p>Set the <code title="dom-SharedWorkerGlobalScope-name"><a href="#dom-sharedworkerglobalscope-name">name</a></code> attribute of
1.81 ihickson 1723: <var title="">worker global scope</var> to <var title="">name</var>.</li>
1.9 ihickson 1724:
1.301 ihickson 1725: <li><p><span>Create a new <code><a href="#messageport">MessagePort</a></code> object</span>
1.81 ihickson 1726: owned by <var title="">worker global scope</var>. Let <var title="">inside port</var> be this new object.</li>
1.9 ihickson 1727:
1.81 ihickson 1728: <li><p><span>Entangle</span> <var title="">outside port</var> and
1729: <var title="">inside port</var>.</li>
1.9 ihickson 1730:
1.155 ihickson 1731: </ol></li>
1.28 ihickson 1732:
1.123 ihickson 1733: <li><p>Return <var title="">worker</var> and perform the remaining
1734: steps asynchronously.</li>
1.18 ihickson 1735:
1.81 ihickson 1736: <li><p>Create an event that uses the <code>MessageEvent</code>
1.118 ihickson 1737: interface, with the name <code title="event-connect">connect</code>, which does not bubble, is not
1.115 ihickson 1738: cancelable, has no default action, has a <code title="dom-MessageEvent-data">data</code> attribute whose value is
1.307 ihickson 1739: initialized to the empty string and has a <code title="dom-MessageEvent-ports">ports</code> attribute whose value
1740: is initialized to a <span title="dfn-read-only-array">read
1741: only</span> array containing only the newly created port, and
1742: <span>queue a task</span> to dispatch the event at <var title="">worker global scope</var>.</li>
1.26 ihickson 1743:
1744: <li>
1.46 ihickson 1745:
1.123 ihickson 1746: <p><a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">Add to
1747: <var title="">worker global scope</var>'s list of <span>the
1748: worker's <code>Document</code>s</span></a> the
1749: <code>Document</code> objects in <var title="">docs</var>.</p>
1750:
1751: </li>
1752:
1753: <li>
1754:
1.192 ihickson 1755: <p>If the <span title="script's global object">global object</span>
1.124 ihickson 1756: of the <span title="concept-script">script</span> that invoked the
1757: constructor is a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, add <var title="">worker global scope</var> to the list of <a href="#the-worker-s-workers">the
1758: worker's workers</a> of the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1.192 ihickson 1759: object that is the <span title="script's global object">global
1760: object</span> of the <span title="concept-script">script</span>
1.124 ihickson 1761: that invoked the constructor.</p>
1762:
1763: </li>
1764:
1765: <li>
1766:
1.159 ihickson 1767: <p><a href="#run-a-worker">Run a worker</a> for <var title="">scriptURL</var>,
1.193 ihickson 1768: with the <span>script's browsing context</span> of the script that
1.159 ihickson 1769: invoked the method as the <var title="">owner browsing
1.232 ihickson 1770: context</var>, with the <span>script's document</span> of the
1771: script that invoked the method as the <var title="">owner
1772: document</var>, with the <span>origin</span> of the <span>entry
1.176 ihickson 1773: script</span> as the <var title="">owner origin</var>, and with
1774: <var title="">worker global scope</var> as the global scope.</p>
1.26 ihickson 1775:
1.60 ihickson 1776: </li>
1.81 ihickson 1777:
1.155 ihickson 1778: </ol><p>This constructor must be visible when the <span>script's global
1.192 ihickson 1779: object</span> is either a <code>Window</code> object or an object
1.155 ihickson 1780: implementing the <code><a href="#workerutils">WorkerUtils</a></code> interface.<p>The <span>task source</span> for the tasks mentioned above is the
1.299 ihickson 1781: <span>DOM manipulation task source</span>.<h2 id="apis-available-to-workers"><span class="secno">5 </span>APIs available to workers</h2><pre class="idl">[NoInterfaceObject]
1.150 ihickson 1782: interface <dfn id="workerutils">WorkerUtils</dfn> {
1.306 ihickson 1783: void <a href="#dom-workerglobalscope-importscripts" title="dom-WorkerGlobalScope-importScripts">importScripts</a>(DOMString... urls);
1.210 ihickson 1784: readonly attribute <a href="#workernavigator">WorkerNavigator</a> <a href="#dom-worker-navigator" title="dom-worker-navigator">navigator</a>;
1.150 ihickson 1785: };
1.290 ihickson 1786: <a href="#workerutils">WorkerUtils</a> implements <span>WindowTimers</span>;
1.301 ihickson 1787: <a href="#workerutils">WorkerUtils</a> implements <span>WindowBase64</span>;</pre><p>The <code>WindowTimers</code> and <code>WindowBase64</code>
1788: interfaces are defined in the HTML specification. <a href="#refsHTML">[HTML]</a><p>The DOM APIs (<code>Node</code> objects, <code>Document</code>
1.81 ihickson 1789: objects, etc) are not available to workers in this version of this
1.155 ihickson 1790: specification.<h3 id="importing-scripts-and-libraries"><span class="secno">5.1 </span>Importing scripts and libraries</h3><p>When a script invokes the <dfn id="dom-workerglobalscope-importscripts" title="dom-WorkerGlobalScope-importScripts"><code>importScripts(<var title="">urls</var>)</code></dfn> method on a
1.115 ihickson 1791: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, the user agent must run the
1.155 ihickson 1792: following steps:<ol><li><p>If there are no arguments, return without doing
1.81 ihickson 1793: anything. Abort these steps.</li>
1794:
1795: <li><p><span title="resolve a url">Resolve</span> each
1796: argument.</li>
1797:
1798: <li><p>If any fail, throw a <code>SYNTAX_ERR</code>
1799: exception.</li>
1800:
1.26 ihickson 1801:
1802: <li>
1.81 ihickson 1803:
1.45 ihickson 1804: <p>Attempt to <span>fetch</span> each resource identified by the
1.194 ihickson 1805: resulting <span title="absolute URL">absolute URLs</span>, from
1.256 ihickson 1806: the <span>entry script</span>'s <span>origin</span>, with the
1.281 ihickson 1807: <i>synchronous flag</i> set.</p>
1.81 ihickson 1808: </li>
1.26 ihickson 1809:
1810: <li>
1811:
1.81 ihickson 1812: <p>For each argument in turn, in the order given, starting with
1813: the first one, run these substeps:</p>
1.26 ihickson 1814:
1.155 ihickson 1815: <ol><li>
1.26 ihickson 1816:
1.81 ihickson 1817: <p>Wait for the fetching attempt for the corresponding resource
1818: to complete.</p>
1.60 ihickson 1819:
1.81 ihickson 1820: <p>If the fetching attempt failed, throw a
1821: <code>NETWORK_ERR</code> exception and abort all these
1822: steps.</p>
1.45 ihickson 1823:
1.264 ihickson 1824: <p>If the attempt succeeds, then let <var title="">source</var> be
1825: the script resource <span>decoded as UTF-8, with error
1826: handling</span>.
1827:
1828: <a href="#refsHTML">[HTML]</a>
1829:
1830: </p>
1.85 ihickson 1831:
1832: <p>Let <var title="">language</var> be JavaScript.</p>
1.61 ihickson 1833:
1.115 ihickson 1834: <p class="note">As with the worker's script, the script here is
1.81 ihickson 1835: always assumed to be JavaScript, regardless of the MIME
1.170 ihickson 1836: type.</p>
1.61 ihickson 1837:
1.81 ihickson 1838: </li>
1.26 ihickson 1839:
1.81 ihickson 1840: <li>
1.26 ihickson 1841:
1.81 ihickson 1842: <p><span>Create a script</span>, using <var title="">source</var> as the script source and <var title="">language</var> as the scripting language, using the
1.189 ihickson 1843: same global object, browsing context, URL character encoding,
1844: base URL, and script group as the <span title="concept-script">script</span> that was created by the
1.115 ihickson 1845: worker's <a href="#run-a-worker">run a worker</a> algorithm.</p>
1.81 ihickson 1846:
1.115 ihickson 1847: <p>Let the newly created <span title="concept-script">script</span> run until it either
1.81 ihickson 1848: returns, fails to parse, fails to catch an exception, or gets
1.115 ihickson 1849: prematurely aborted by the "<a href="#kill-a-worker">kill a worker</a>" or
1850: "<a href="#terminate-a-worker">terminate a worker</a>" algorithms defined above.</p>
1.26 ihickson 1851:
1.199 ihickson 1852: <p>If it failed to parse, then throw an ECMAScript
1853: <code>SyntaxError</code> exception and abort all these
1854: steps. <a href="#refsECMA262">[ECMA262]</a></p>
1.63 ihickson 1855:
1.81 ihickson 1856: <p>If an exception was raised or if the script was prematurely
1857: aborted, then abort all these steps, letting the exception or
1858: aborting continue to be processed by the script that called the
1.115 ihickson 1859: <code title="dom-WorkerGlobalScope-importScripts"><a href="#dom-workerglobalscope-importscripts">importScripts()</a></code>
1.81 ihickson 1860: method.</p>
1861:
1.115 ihickson 1862: <p>If the "<a href="#kill-a-worker">kill a worker</a>" or "<a href="#terminate-a-worker">terminate a
1.81 ihickson 1863: worker</a>" algorithms abort the script then abort all these
1864: steps.</p>
1865:
1866: </li>
1867:
1.155 ihickson 1868: </ol></li>
1.152 ihickson 1869:
1.210 ihickson 1870: </ol><h3 id="the-workernavigator-object"><span class="secno">5.2 </span>The <code><a href="#workernavigator">WorkerNavigator</a></code> object</h3><p>The <dfn id="dom-worker-navigator" title="dom-worker-navigator"><code>navigator</code></dfn> attribute
1.115 ihickson 1871: of the <code><a href="#workerutils">WorkerUtils</a></code> interface must return an instance of
1.210 ihickson 1872: the <code><a href="#workernavigator">WorkerNavigator</a></code> interface, which represents the
1873: identity and state of the user agent (the client):<pre class="idl">interface <dfn id="workernavigator">WorkerNavigator</dfn> {};
1874: <a href="#workernavigator">WorkerNavigator</a> implements <span>NavigatorID</span>;
1875: <a href="#workernavigator">WorkerNavigator</a> implements <span>NavigatorOnLine</span>;</pre><p>Objects implementing the <code><a href="#workernavigator">WorkerNavigator</a></code> interface
1876: also implement the <code>NavigatorID</code> and
1877: <code>NavigatorOnLine</code> interfaces.
1.205 ihickson 1878:
1.226 ihickson 1879: <a href="#refsHTML">[HTML]</a>
1.205 ihickson 1880:
1.210 ihickson 1881: <p>This <code><a href="#workernavigator">WorkerNavigator</a></code> interface must not exist if the
1882: interface's <span>relevant namespace object</span> is a
1.272 ihickson 1883: <code>Window</code> object. <a href="#refsWEBIDL">[WEBIDL]</a><h3 id="interface-objects-and-constructors"><span class="secno">5.3 </span>Interface objects and constructors</h3><p>There must be no interface objects and constructors available in
1.192 ihickson 1884: the global scope of scripts whose <span>script's global
1885: object</span> is a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object except for
1.155 ihickson 1886: the following:<ul><li><p><code>XMLHttpRequest</code> and all interface objects and
1.81 ihickson 1887: constructors defined by the XMLHttpRequest specifications, except
1888: that the <span>document response entity body</span> must always be
1.160 ihickson 1889: null. The <span><code>XMLHttpRequest</code> base URL</span> is the
1890: <span>script's base URL</span>; the
1891: <span><code>XMLHttpRequest</code> origin</span> is the script's
1892: <span>origin</span>. <a href="#refsXHR">[XHR]</a></li>
1.81 ihickson 1893:
1.205 ihickson 1894: <li><p>The interface objects and constructors defined by this
1895: specification.</li>
1.119 ihickson 1896:
1.205 ihickson 1897: <li><p>Constructors defined by specifications that explicitly say
1898: that they should be visible when the <span>script's global
1899: object</span> is a <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>, a
1900: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>, or an object implementing the
1901: <code><a href="#workerutils">WorkerUtils</a></code> interface; the interfaces of any objects
1902: with such constructors; and the interfaces of any objects made
1903: accessible through APIs exposed by those constructors or made
1904: accessible through interfaces to be implemented by any objects that
1905: are themselves accessible to scripts whose <span>script's global
1906: object</span> implements the <code><a href="#workerutils">WorkerUtils</a></code>
1907: interface.</li>
1908:
1909: </ul><p class="note">These requirements do not override the requirements
1910: defined by the Web IDL specification, in particular concerning the
1.272 ihickson 1911: visibility of interfaces annotated with the <code title="">[NoInterfaceObject]</code> extended attribute.<h3 id="worker-locations"><span class="secno">5.4 </span>Worker locations</h3><pre class="idl">interface <dfn id="workerlocation">WorkerLocation</dfn> {
1.263 ihickson 1912: // <span>URL decomposition IDL attributes</span>
1.294 ihickson 1913: stringifier readonly attribute DOMString <a href="#dom-workerlocation-href" title="dom-WorkerLocation-href">href</a>;
1.115 ihickson 1914: readonly attribute DOMString <a href="#dom-workerlocation-protocol" title="dom-WorkerLocation-protocol">protocol</a>;
1915: readonly attribute DOMString <a href="#dom-workerlocation-host" title="dom-WorkerLocation-host">host</a>;
1916: readonly attribute DOMString <a href="#dom-workerlocation-hostname" title="dom-WorkerLocation-hostname">hostname</a>;
1917: readonly attribute DOMString <a href="#dom-workerlocation-port" title="dom-WorkerLocation-port">port</a>;
1918: readonly attribute DOMString <a href="#dom-workerlocation-pathname" title="dom-WorkerLocation-pathname">pathname</a>;
1919: readonly attribute DOMString <a href="#dom-workerlocation-search" title="dom-WorkerLocation-search">search</a>;
1920: readonly attribute DOMString <a href="#dom-workerlocation-hash" title="dom-WorkerLocation-hash">hash</a>;
1.155 ihickson 1921: };</pre><p>A <code><a href="#workerlocation">WorkerLocation</a></code> object represents an <span>absolute
1922: URL</span> set at its creation.<p>The <dfn id="dom-workerlocation-href" title="dom-WorkerLocation-href"><code>href</code></dfn>
1.81 ihickson 1923: attribute must return the <span>absolute URL</span> that the object
1.155 ihickson 1924: represents.<p>The <code><a href="#workerlocation">WorkerLocation</a></code> interface also has the complement
1.163 ihickson 1925: of <span>URL decomposition IDL attributes</span>, <dfn id="dom-workerlocation-protocol" title="dom-WorkerLocation-protocol"><code>protocol</code></dfn>,
1.115 ihickson 1926: <dfn id="dom-workerlocation-host" title="dom-WorkerLocation-host"><code>host</code></dfn>, <dfn id="dom-workerlocation-port" title="dom-WorkerLocation-port"><code>port</code></dfn>, <dfn id="dom-workerlocation-hostname" title="dom-WorkerLocation-hostname"><code>hostname</code></dfn>,
1927: <dfn id="dom-workerlocation-pathname" title="dom-WorkerLocation-pathname"><code>pathname</code></dfn>,
1928: <dfn id="dom-workerlocation-search" title="dom-WorkerLocation-search"><code>search</code></dfn>,
1.263 ihickson 1929: and <dfn id="dom-workerlocation-hash" title="dom-WorkerLocation-hash"><code>hash</code></dfn>.
1930: These must follow the rules given for <span>URL decomposition IDL
1931: attributes</span>, with the <span title="concept-uda-input">input</span> being the <span>absolute
1932: URL</span> that the object represents (same as the <code title="dom-WorkerLocation-href"><a href="#dom-workerlocation-href">href</a></code> attribute), and the
1933: <span title="concept-uda-setter">common setter action</span> being a
1934: no-op, since the attributes are defined to be readonly.
1.205 ihickson 1935:
1.226 ihickson 1936: <a href="#refsHTML">[HTML]</a>
1.205 ihickson 1937:
1.209 ihickson 1938: <p>The <code><a href="#workerlocation">WorkerLocation</a></code> interface must not exist if the
1939: interface's <span>relevant namespace object</span> is a
1.281 ihickson 1940: <code>Window</code> object. <a href="#refsWEBIDL">[WEBIDL]</a><h2 class="no-num" id="references">References</h2><p>All references are normative unless marked "Non-normative".</p><dl><dt id="refsDOMCORE">[DOMCORE]</dt>
1.276 ihickson 1941: <dd><cite><a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html">Web DOM Core</a></cite>, A. van Kesteren. W3C.</dd>
1.153 ihickson 1942:
1.152 ihickson 1943: <dt id="refsECMA262">[ECMA262]</dt>
1944: <dd><cite><a href="http://www.ecma-international.org/publications/standards/Ecma-262.htm">ECMAScript
1.226 ihickson 1945: Language Specification</a></cite>. ECMA.</dd>
1.152 ihickson 1946:
1.226 ihickson 1947: <dt id="refsHTML">[HTML]</dt>
1948: <dd><cite><a href="http://www.whatwg.org/specs/web-apps/current-work/">HTML</a></cite>,
1949: I. Hickson. WHATWG.</dd>
1.152 ihickson 1950:
1.154 ihickson 1951: <dt id="refsRFC2119">[RFC2119]</dt>
1.265 ihickson 1952: <dd><cite><a href="http://tools.ietf.org/html/rfc2119">Key words for use in
1.226 ihickson 1953: RFCs to Indicate Requirement Levels</a></cite>, S. Bradner. IETF.</dd>
1.154 ihickson 1954:
1955: <dt id="refsWEBIDL">[WEBIDL]</dt>
1.281 ihickson 1956: <dd><cite><a href="http://dev.w3.org/2006/webapi/WebIDL/">Web
1.226 ihickson 1957: IDL</a></cite>, C. McCormack. W3C.</dd>
1.154 ihickson 1958:
1.152 ihickson 1959: <dt id="refsXHR">[XHR]</dt>
1.281 ihickson 1960: <dd><cite><a href="http://dev.w3.org/2006/webapi/XMLHttpRequest-2/"><code>XMLHttpRequest</code></a></cite>,
1.226 ihickson 1961: A. van Kesteren. W3C.</dd>
1.152 ihickson 1962:
1.221 ihickson 1963: </dl><h2 class="no-num" id="acknowledgements">Acknowledgements</h2><!-- ACKS --><p>Thanks to
1.81 ihickson 1964:
1965: Aaron Boodman,
1.155 ihickson 1966: Алексей Проскуряков (Alexey Proskuryakov),
1.81 ihickson 1967: Anne van Kesteren,
1968: Ben Turner,
1969: Dmitry Titov,
1.96 ihickson 1970: Drew Wilson,
1.97 ihickson 1971: Jeremy Orlow,
1.81 ihickson 1972: Jonas Sicking,
1973: Justin James,
1974: Kevin Hakanson,
1975: Maciej Stachowiak,
1976: Michael Nordman,
1977: Mike Smith,
1978:
1979: and
1980:
1981: Philip Taylor
1982:
1.155 ihickson 1983: for their useful and substantial comments.<p>Huge thanks to the whole Gears team, who pioneered this
1.81 ihickson 1984: technology and whose experience has been a huge influence on this
1.155 ihickson 1985: specification.
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