Annotation of html5/workers/Overview.html, revision 1.178
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1.82 ihickson 66:
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1.155 ihickson 167: </style><link href="http://www.w3.org/StyleSheets/TR/W3C-ED" rel="stylesheet" type="text/css"><!-- ZZZ ED vs WD --><div class="head">
1.115 ihickson 168: <p><a href="http://www.w3.org/"><img alt="W3C" height="48" src="http://www.w3.org/Icons/w3c_home" width="72"></a></p>
1.54 ihickson 169: <h1>Web Workers</h1>
1.109 ihickson 170: <!--ZZZ:-->
1.117 ihickson 171: <!--<h2 class="no-num no-toc">W3C Working Draft 23 April 2009</h2>-->
1.178 ! ihickson 172: <h2 class="no-num no-toc" id="editor-s-draft-4-october-2009">Editor's Draft 4 October 2009</h2>
1.109 ihickson 173: <!--:ZZZ-->
1.155 ihickson 174: <dl><!-- ZZZ: update the month/day (twice), (un)comment out
1.117 ihickson 175: <dt>This Version:</dt>
1.115 ihickson 176: <dd><a href="http://www.w3.org/TR/2009/WD-workers-20090423/">http://www.w3.org/TR/2009/WD-workers-20090423/</a></dd>
1.155 ihickson 177: :ZZZ --><dt>Latest Published Version:</dt>
1.115 ihickson 178: <dd><a href="http://www.w3.org/TR/workers/">http://www.w3.org/TR/workers/</a></dd>
1.109 ihickson 179: <dt>Latest Editor's Draft:</dt>
1.115 ihickson 180: <dd><a href="http://dev.w3.org/html5/workers/">http://dev.w3.org/html5/workers/</a></dd>
1.117 ihickson 181: <!-- ZZZ: add the new version after it has shipped-->
1.2 ihickson 182: <dt>Previous Versions:</dt>
1.113 ihickson 183: <dd><a href="http://www.w3.org/TR/2009/WD-workers-20090423/">http://www.w3.org/TR/2009/WD-workers-20090423/</a>
1.117 ihickson 184: <!-- :ZZZ -->
1.81 ihickson 185: <dt>Editors:</dt>
1.115 ihickson 186: <dd><a href="mailto:ian@hixie.ch">Ian Hickson</a>, Google, Inc.</dd>
1.155 ihickson 187: </dl><p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a>
188: © 2009 <a href="http://www.w3.org/"><abbr title="World Wide
189: Web Consortium">W3C</abbr></a><sup>®</sup> (<a href="http://www.csail.mit.edu/"><abbr title="Massachusetts
1.115 ihickson 190: Institute of Technology">MIT</abbr></a>, <a href="http://www.ercim.org/"><abbr title="European Research
191: Consortium for Informatics and Mathematics">ERCIM</abbr></a>, <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C
192: <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
193: <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a>
194: and <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document
1.81 ihickson 195: use</a> rules apply.</p>
1.155 ihickson 196: </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 197: authors to spawn background workers running scripts in parallel to
198: their main page. This allows for thread-like operation with
1.155 ihickson 199: message-passing as the coordination mechanism.<h2 class="no-num no-toc" id="status-of-this-document">Status of this document</h2><!-- intro boilerplate (required) --><p><em>This section describes the status of this document at the
1.81 ihickson 200: time of its publication. Other documents may supersede this
201: document. A list of current W3C publications and the most recently
202: formally published revision of this technical report can be found in
1.115 ihickson 203: the <a href="http://www.w3.org/TR/">W3C technical reports index</a>
1.155 ihickson 204: at http://www.w3.org/TR/.</em></p><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- XXX this section will be moved back to just below the copyright
1.116 ihickson 205: notice in the header by October 2009 unless the spec as a whole has
1.155 ihickson 206: been transitioned to a more permissive license by that time. --><!-- XXX when moving this text, add: class="alt copyright" --><p>The <a href="http://www.whatwg.org/specs/web-workers/current-work/">WHATWG
1.116 ihickson 207: version</a> of this specification is available under a license that
1.155 ihickson 208: permits reuse of the specification text.</p><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- where to send feedback (required) --><p>If you wish to make comments regarding this document, please send
1.115 ihickson 209: them to <a href="mailto:public-webapps@w3.org">public-webapps@w3.org</a>
1.90 ihickson 210: (<a href="mailto:public-webapps-request@w3.org?subject=subscribe">subscribe</a>,
1.115 ihickson 211: <a href="http://lists.w3.org/Archives/Public/public-webapps/">archives</a>)
1.81 ihickson 212:
213: <!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING SENTENCE TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
1.115 ihickson 214: or <a href="mailto:whatwg@whatwg.org">whatwg@whatwg.org</a> (<a href="http://lists.whatwg.org/listinfo.cgi/whatwg-whatwg.org">subscribe</a>,
215: <a href="http://lists.whatwg.org/pipermail/whatwg-whatwg.org/">archives</a>).
1.110 ihickson 216: <!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING SENTENCE TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST -->
1.1 ihickson 217:
1.155 ihickson 218: All feedback is welcome.</p><!-- stability (required) --><p>Implementors should be aware that this specification is not
1.81 ihickson 219: stable. <strong>Implementors who are not taking part in the
220: discussions are likely to find the specification changing out from
221: under them in incompatible ways.</strong> Vendors interested in
222: implementing this specification before it eventually reaches the
223: Candidate Recommendation stage should join the aforementioned
1.155 ihickson 224: mailing lists and take part in the discussions.</p><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- version history or list of changes (required) --><p>The latest stable version of the editor's draft of this
1.115 ihickson 225: specification is always available on <a href="http://dev.w3.org/html5/workers/Overview.html">the W3C CVS
226: server</a> and in the <a href="http://svn.whatwg.org/webworkers/">WHATWG Subversion
1.81 ihickson 227: repository</a>. The latest editor's working copy (which may contain
1.115 ihickson 228: unfinished text in the process of being prepared) is available <a href="http://www.whatwg.org/specs/web-workers/current-work/">on the
1.81 ihickson 229: WHATWG site</a>. Detailed change history can be obtained from the
1.155 ihickson 230: following locations:</p><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING LIST TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><ul><li>Twitter messages (non-editorial changes only): <a href="http://twitter.com/WHATWG">http://twitter.com/WHATWG</a></li>
1.115 ihickson 231: <li>Interactive Web interface: <a href="http://html5.org/tools/web-workers-tracker">http://html5.org/tools/web-workers-tracker</a></li>
232: <li>Commit-Watchers mailing list: <a href="http://lists.whatwg.org/listinfo.cgi/commit-watchers-whatwg.org">http://lists.whatwg.org/listinfo.cgi/commit-watchers-whatwg.org</a></li>
233: <li>Subversion interface: <a href="http://svn.whatwg.org/webworkers/">http://svn.whatwg.org/webworkers/</a></li>
234: <li>CVS log: <a href="http://dev.w3.org/cvsweb/html5/workers/Overview.html">http://dev.w3.org/cvsweb/html5/workers/Overview.html</a></li>
1.155 ihickson 235: </ul><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING LIST TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- status of document, group responsible (required) --><p>The W3C <a href="http://www.w3.org/2008/webapps/">Web Apps
1.81 ihickson 236: Working Group</a> is the W3C working group responsible for this
237: specification's progress along the W3C Recommendation track.
238: <!--ZZZ:-->
1.117 ihickson 239: <!--This specification is the 23 April 2009 Working Draft.-->
1.178 ! ihickson 240: This specification is the 4 October 2009 Editor's Draft.
1.81 ihickson 241: <!--:ZZZ-->
1.155 ihickson 242: </p><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- relationship to other work (required) --><p>This specification is also being produced by the <a href="http://www.whatwg.org/">WHATWG</a>. The two specifications are
243: identical from the table of contents onwards.</p><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- context and rationale (required) --><p>This specification is intended to specify a part of the Web
1.81 ihickson 244: platform closely related to HTML5. It is defined in a separate
1.155 ihickson 245: document primarily to ease the cognitive load on reviewers.</p><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- required patent boilerplate --><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 246: 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 247: any patent disclosures</a> made in connection with the deliverables
248: of the group; that page also includes instructions for disclosing a
249: patent. An individual who has actual knowledge of a patent which the
1.115 ihickson 250: individual believes contains <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential
251: Claim(s)</a> must disclose the information in accordance with <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section
1.155 ihickson 252: 6 of the W3C Patent Policy</a>.<h2 class="no-num no-toc" id="contents">Table of contents</h2>
1.81 ihickson 253: <!--begin-toc-->
1.115 ihickson 254: <ol class="toc">
255: <li><a href="#introduction"><span class="secno">1 </span>Introduction</a>
1.81 ihickson 256: <ol>
1.115 ihickson 257: <li><a href="#scope"><span class="secno">1.1 </span>Scope</a></li>
258: <li><a href="#tutorial"><span class="secno">1.2 </span>Tutorial</a>
1.81 ihickson 259: <ol>
1.115 ihickson 260: <li><a href="#a-background-number-crunching-worker"><span class="secno">1.2.1 </span>A background number-crunching worker</a></li>
261: <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>
262: <li><a href="#worker-used-for-background-i-o"><span class="secno">1.2.3 </span>Worker used for background I/O</a></li>
263: <li><a href="#shared-workers"><span class="secno">1.2.4 </span>Shared workers</a></li>
264: <li><a href="#delegation"><span class="secno">1.2.5 </span>Delegation</a></li>
265: <li><a href="#providing-libraries"><span class="secno">1.2.6 </span>Providing libraries</a></ol></ol></li>
1.148 ihickson 266: <li><a href="#conformance-requirements"><span class="secno">2 </span>Conformance requirements</a>
1.82 ihickson 267: <ol>
1.148 ihickson 268: <li><a href="#dependencies"><span class="secno">2.1 </span>Dependencies</a></ol></li>
269: <li><a href="#terminology"><span class="secno">3 </span>Terminology</a></li>
270: <li><a href="#infrastructure"><span class="secno">4 </span>Infrastructure</a>
271: <ol>
272: <li><a href="#the-global-scope"><span class="secno">4.1 </span>The global scope</a>
1.81 ihickson 273: <ol>
1.148 ihickson 274: <li><a href="#the-workerglobalscope-abstract-interface"><span class="secno">4.1.1 </span>The <code>WorkerGlobalScope</code> abstract interface</a></li>
275: <li><a href="#dedicated-workers-and-the-dedicatedworkerglobalscope-interface"><span class="secno">4.1.2 </span>Dedicated workers and the <code>DedicatedWorkerGlobalScope</code> interface</a></li>
276: <li><a href="#shared-workers-and-the-sharedworkerglobalscope-inteface"><span class="secno">4.1.3 </span>Shared workers and the <code>SharedWorkerGlobalScope</code> inteface</a></ol></li>
1.160 ihickson 277: <li><a href="#origins-of-workers"><span class="secno">4.2 </span>Origins of workers</a></li>
1.148 ihickson 278: <li><a href="#decoding-scripts"><span class="secno">4.3 </span>Decoding scripts</a></li>
279: <li><a href="#the-event-loop"><span class="secno">4.4 </span>The event loop</a></li>
280: <li><a href="#the-worker-s-lifetime"><span class="secno">4.5 </span>The worker's lifetime</a></li>
281: <li><a href="#processing-model"><span class="secno">4.6 </span>Processing model</a></li>
282: <li><a href="#runtime-script-errors"><span class="secno">4.7 </span>Runtime script errors</a></li>
283: <li><a href="#creating-workers"><span class="secno">4.8 </span>Creating workers</a>
1.81 ihickson 284: <ol>
1.148 ihickson 285: <li><a href="#the-abstractworker-abstract-interface"><span class="secno">4.8.1 </span>The <code>AbstractWorker</code> abstract interface</a></li>
286: <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>
287: <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>
288: <li><a href="#apis-available-to-workers"><span class="secno">5 </span>APIs available to workers</a>
1.81 ihickson 289: <ol>
1.148 ihickson 290: <li><a href="#importing-scripts-and-libraries"><span class="secno">5.1 </span>Importing scripts and libraries</a></li>
291: <li><a href="#the-navigator-object"><span class="secno">5.2 </span>The <code title="worker-Navigator">Navigator</code> object</a></li>
292: <li><a href="#apis-defined-in-other-specifications"><span class="secno">5.3 </span>APIs defined in other specifications</a></li>
293: <li><a href="#interface-objects-and-constructors"><span class="secno">5.4 </span>Interface objects and constructors</a></li>
294: <li><a href="#worker-locations"><span class="secno">5.5 </span>Worker locations</a></ol></li>
1.115 ihickson 295: <li><a class="no-num" href="#references">References</a></li>
296: <li><a class="no-num" href="#acknowledgements">Acknowledgements</a></ol>
1.155 ihickson 297: <!--end-toc--><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
298: background independently of any user interface scripts.<p>This allows for long-running scripts that are not interrupted by
1.81 ihickson 299: scripts that respond to clicks or other user interactions, and
300: allows long tasks to be executed without yielding to keep the page
1.155 ihickson 301: responsive.<p>Workers (as these background scripts are called herein) are
1.81 ihickson 302: relatively heavy-weight, and are not intended to be used in large
303: numbers. For example, it would be inappropriate to launch one worker
304: for each pixel of a four megapixel image. The examples below show
1.155 ihickson 305: some appropriate uses of workers.<p>Generally, workers are expected to be long-lived, have a high
306: start-up performance cost, and a high per-instance memory cost.<h3 id="tutorial"><span class="secno">1.2 </span>Tutorial</h3><p><i>This section is non-normative.</i><p>There are a variety of uses that workers can be put to. The
307: 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
308: expensive task without interrupting the user interface.<p>In this example, the main document spawns a worker to
309: (naïvely) compute prime numbers, and progressively displays the
310: most recently found prime number.<p>The main page is as follows:<pre><!DOCTYPE HTML>
1.81 ihickson 311: <html>
312: <head>
313: <title>Worker example: One-core computation</title>
314: </head>
315: <body>
316: <p>The highest prime number discovered so far is: <output id="result"></output></p>
317: <script>
1.50 ihickson 318: var worker = new Worker('worker.js');
319: worker.onmessage = function (event) {
1.54 ihickson 320: document.getElementById('result').textContent = event.data;
1.29 ihickson 321: };
1.81 ihickson 322: </script>
323: </body>
1.155 ihickson 324: </html></pre><p>The <code title="dom-Worker"><a href="#dom-worker">Worker()</a></code> constructor call
1.115 ihickson 325: creates a worker and returns a <code><a href="#worker">Worker</a></code> object
1.81 ihickson 326: representing that worker, which is used to communicate with the
1.177 ihickson 327: 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 328: search: while (true) {
329: n += 1;
330: for (var i = 2; i <= Math.sqrt(n); i += 1)
331: if (n % i == 0)
332: continue search;
333: // found a prime!
1.50 ihickson 334: postMessage(n);
1.155 ihickson 335: }</pre><p>The bulk of this code is simply an unoptimized search for a prime
1.115 ihickson 336: number. To send a message back to the page, the <code title="dom-DedicatedWorkerGlobalScope-postMessage"><a href="#dom-dedicatedworkerglobalscope-postmessage">postMessage()</a></code>
1.155 ihickson 337: method is used to post a message when a prime is 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 338: task is to listen for notifications from the server, and, when
339: appropriate, either add or remove data from the client-side
1.155 ihickson 340: database.<p>Since no communication occurs between the worker and the main
341: page, the main page can start the worker by just doing:<pre><script>
1.50 ihickson 342: new Worker('worker.js');
1.155 ihickson 343: </script></pre><p>The worker itself is as follows:<pre>var server = new WebSocket('ws://whatwg.org/database');
1.42 ihickson 344: var database = openDatabase('demobase', '1.0', 'Demo Database', 10240);
1.31 ihickson 345: server.onmessage = function (event) {
346: // data is in the format "command key value"
1.54 ihickson 347: var data = event.data.split(' ');
1.31 ihickson 348: switch (data[0]) {
349: case '+':
350: database.transaction(function(tx) {
351: tx.executeSql('INSERT INTO pairs (key, value) VALUES (?, ?)', data[1], data[2]);
352: });
353: case '-':
354: database.transaction(function(tx) {
355: tx.executeSql('DELETE FROM pairs WHERE key=? AND value=?', data[1], data[2]);
356: });
357: }
1.155 ihickson 358: };</pre><p>This connects to the server using the <code>WebSocket</code>
1.81 ihickson 359: mechanism and opens the local database (which, we presume, has been
360: created earlier). The worker then just listens for messages from the
361: server and acts on them as appropriate, forever (or until the main
1.155 ihickson 362: page is closed).<p><a href="http://www.whatwg.org/demos/workers/database-updater/page.html">View
1.81 ihickson 363: this example online</a>. (This example will not actually function,
364: since the server does not actually exist and the database is not
1.155 ihickson 365: 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 366: fetching stock updates for at regular intervals, and one for
1.155 ihickson 367: fetching performing search queries that the user requests.<p>The main page is as follows:<pre><!DOCTYPE HTML>
1.81 ihickson 368: <html>
369: <head>
370: <title>Worker example: Stock ticker</title>
371: <script>
1.33 ihickson 372: // TICKER
373: var symbol = 'GOOG'; // default symbol to watch
1.50 ihickson 374: var ticker = new Worker('ticker.js');
1.33 ihickson 375:
376: // SEARCHER
1.50 ihickson 377: var searcher = new Worker('searcher.js');
1.33 ihickson 378: function search(query) {
1.50 ihickson 379: searcher.postMessage(query);
1.33 ihickson 380: }
381:
382: // SYMBOL SELECTION UI
383: function select(newSymbol) {
384: symbol = newSymbol;
1.50 ihickson 385: ticker.postMessage(symbol);
1.33 ihickson 386: }
1.81 ihickson 387: </script>
388: </head>
1.122 ihickson 389: <body onload="search('')">
1.81 ihickson 390: <p><output id="symbol"></output> <output id="value"></output></p>
391: <script>
1.50 ihickson 392: ticker.onmessage = function (event) {
1.54 ihickson 393: var data = event.data.split(' ');
1.33 ihickson 394: document.getElementById('symbol').textContent = data[0];
395: document.getElementById('value').textContent = data[1];
396: };
1.50 ihickson 397: ticker.postMessage(symbol);
1.81 ihickson 398: </script>
1.122 ihickson 399: <p><label>Search: <input type="text" autofocus oninput="search(this.value)"></label></p>
1.81 ihickson 400: <ul id="results"></ul>
401: <script>
1.50 ihickson 402: searcher.onmessage = function (event) {
1.54 ihickson 403: var data = event.data.split(' ');
1.33 ihickson 404: var results = document.getElementById('results');
405: while (results.hasChildNodes()) // clear previous results
406: results.removeChild(results.firstChild);
407: for (var i = 0; i < data.length; i += 1) {
408: // add a list item with a button for each result
409: var li = document.createElement('li');
410: var button = document.createElement('button');
411: button.value = data[i];
412: button.type = 'button';
413: button.onclick = function () { select(this.value); };
414: button.textContent = data[i];
415: li.appendChild(button);
416: results.appendChild(li);
417: }
418: };
1.81 ihickson 419: </script>
420: <p>(The data in this example is not real. Try searching for "Google" or "Apple".)</p>
421: </body>
1.155 ihickson 422: </html></pre><p>The two workers use a common library for performing the actual
423: network calls. This library is as follows:<pre>function get(url) {
1.50 ihickson 424: try {
425: var xhr = new XMLHttpRequest();
426: xhr.open('GET', url, false);
427: xhr.send();
428: return xhr.responseText;
429: } catch (e) {
430: return ''; // turn all errors into empty results
431: }
1.155 ihickson 432: }</pre><p>The stock updater worker is as follows:<pre>importScripts('io.js');
1.33 ihickson 433: var timer;
434: var symbol;
435: function update() {
1.50 ihickson 436: postMessage(symbol + ' ' + get('stock.cgi?' + symbol));
1.33 ihickson 437: timer = setTimeout(update, 10000);
438: }
1.50 ihickson 439: onmessage = function (event) {
1.33 ihickson 440: if (timer)
441: clearTimeout(timer);
1.54 ihickson 442: symbol = event.data;
1.33 ihickson 443: update();
1.155 ihickson 444: };</pre><p>The search query worker is as follows:<pre>importScripts('io.js');
1.50 ihickson 445: onmessage = function (event) {
1.54 ihickson 446: postMessage(get('search.cgi?' + event.data));
1.155 ihickson 447: };</pre><p><a href="http://www.whatwg.org/demos/workers/stocks/page.html">View this example online</a>.<h4 id="shared-workers"><span class="secno">1.2.4 </span>Shared workers</h4><p><i>This section is non-normative.</i><p>In this example, multiple windows (viewers) can be opened that
1.81 ihickson 448: are all viewing the same map. All the windows share the same map
449: information, with a single worker coordinating all the viewers. Each
450: viewer can move around independently, but if they set any data on
1.155 ihickson 451: the map, all the viewers are updated.<p>The main page isn't interesting, it merely provides a way to open
452: the viewers:<pre><!DOCTYPE HTML>
1.81 ihickson 453: <html>
454: <head>
455: <title>Workers example: Multiviewer</title>
456: <script>
1.36 ihickson 457: function openViewer() {
458: window.open('viewer.html');
459: }
1.81 ihickson 460: </script>
461: </head>
462: <body>
463: <p><button type=button onclick="openViewer()">Open a new
464: viewer</button></p>
465: <p>Each viewer opens in a new window. You can have as many viewers
466: as you like, they all view the same data.</p>
467: </body>
1.155 ihickson 468: </html></pre><p>The viewer is more involved:<pre><!DOCTYPE HTML>
1.81 ihickson 469: <html>
470: <head>
471: <title>Workers example: Multiviewer viewer</title>
472: <script>
1.50 ihickson 473: var worker = new SharedWorker('worker.js', 'core');
1.36 ihickson 474:
475: // CONFIGURATION
476: function configure(event) {
1.54 ihickson 477: if (event.data.substr(0, 4) != 'cfg ') return;
478: var name = event.data.substr(4).split(' ', 1);
1.36 ihickson 479: // update display to mention our name is name
480: document.getElementsByTagName('h1')[0].textContent += ' ' + name;
481: // no longer need this listener
1.43 ihickson 482: worker.port.removeEventListener('message', configure, false);
1.36 ihickson 483: }
1.53 ihickson 484: worker.port.addEventListener('message', configure, false);
1.36 ihickson 485:
486: // MAP
487: function paintMap(event) {
1.54 ihickson 488: if (event.data.substr(0, 4) != 'map ') return;
489: var data = event.data.substr(4).split(',');
1.36 ihickson 490: // display tiles data[0] .. data[8]
491: var canvas = document.getElementById('map');
492: var context = canvas.getContext('2d');
493: for (var y = 0; y < 3; y += 1) {
494: for (var x = 0; x < 3; x += 1) {
495: var tile = data[y * 3 + x];
496: if (tile == '0')
497: context.fillStyle = 'green';
498: else
499: context.fillStyle = 'maroon';
500: fillRect(x * 50, y * 50, 50, 50);
501: }
502: }
503: }
1.53 ihickson 504: worker.port.addEventListener('message', paintMap, false);
1.36 ihickson 505:
506: // PUBLIC CHAT
507: function updatePublicChat(event) {
1.54 ihickson 508: if (event.data.substr(0, 4) != 'txt ') return;
509: var name = event.data.substr(4).split(' ', 1);
510: var message = event.data.substr(4 + length(name) + 1);
1.81 ihickson 511: // display "<name> message" in public chat
1.36 ihickson 512: var dialog = document.getElementById('public');
513: var dt = document.createElement('dt');
514: dt.textContent = name;
515: dialog.appendChild(dt);
516: var dd = document.createElement('dd');
517: dd.textContent = message;
518: dialog.appendChild(dd);
519: }
1.53 ihickson 520: worker.port.addEventListener('message', updatePublicChat, false);
1.36 ihickson 521:
522: // PRIVATE CHAT
523: function startPrivateChat(event) {
1.54 ihickson 524: if (event.data.substr(0, 4) != 'msg ') return;
525: var name = event.data.substr(4).split(' ', 1);
1.84 ihickson 526: var port = event.ports[0];
1.36 ihickson 527: // display a private chat UI
528: var ul = document.getElementById('private');
529: var li = document.createElement('li');
530: var h3 = document.createElement('h3');
531: h3.textContent = 'Private chat with ' + name;
532: li.appendChild(h3);
533: var dialog = document.createElement('dialog');
534: var addMessage = function(name, message) {
535: var dt = document.createElement('dt');
536: dt.textContent = name;
537: dialog.appendChild(dt);
538: var dd = document.createElement('dd');
539: dd.textContent = message;
540: dialog.appendChild(dd);
541: };
542: port.onmessage = function (event) {
1.54 ihickson 543: addMessage(name, event.data);
1.36 ihickson 544: };
545: li.appendChild(dialog);
546: var form = document.createElement('form');
547: var p = document.createElement('p');
548: var input = document.createElement('input');
549: input.size = 50;
550: p.appendChild(input);
551: p.appendChild(document.createTextNode(' '));
552: var button = document.createElement('button');
553: button.textContent = 'Post';
554: p.appendChild(button);
555: form.onsubmit = function () {
556: port.postMessage(input.value);
557: addMessage('me', input.value);
558: input.value = '';
559: return false;
560: };
561: form.appendChild(p);
562: li.appendChild(form);
563: }
1.53 ihickson 564: worker.port.addEventListener('message', startPrivateChat, false);
1.81 ihickson 565: </script>
566: </head>
567: <body>
568: <h1>Viewer</h1>
569: <h2>Map</h2>
570: <p><canvas id="map" height=150 width=150></canvas></p>
571: <p>
572: <button type=button onclick="worker.port.postMessage('mov left')">Left</button>
573: <button type=button onclick="worker.port.postMessage('mov up')">Up</button>
574: <button type=button onclick="worker.port.postMessage('mov down')">Down</button>
575: <button type=button onclick="worker.port.postMessage('mov right')">Right</button>
576: <button type=button onclick="worker.port.postMessage('set 0')">Set 0</button>
577: <button type=button onclick="worker.port.postMessage('set 1')">Set 1</button>
578: </p>
579: <h2>Public Chat</h2>
580: <dialog id="public"></dialog>
581: <form onsubmit="worker.port.postMessage('txt ' + message.value); message.value = ''; return false;">
582: <p>
583: <input type="text" name="message" size="50">
584: <button>Post</button>
585: </p>
586: </form>
587: <h2>Private Chat</h2>
588: <ul id="private"></ul>
589: </body>
590: </html>
1.155 ihickson 591: </pre><p>There are several key things worth noting about the way the
592: viewer is written.<p><strong>Multiple listeners</strong>. Instead of a single message
1.81 ihickson 593: processing function, the code here attaches multiple event
594: listeners, each one performing a quick check to see if it is
595: relevant for the message. In this example it doesn't make much
596: difference, but if multiple authors wanted to collaborate using a
597: single port to communicate with a worker, it would allow for
598: independent code instead of changes having to all be made to a
1.155 ihickson 599: single event handling function.<p>Registering event listeners in this way also allows you to
1.81 ihickson 600: unregister specific listeners when you are done with them, as is
601: done with the <code title="">configure()</code> method in this
1.155 ihickson 602: example.<p>Finally, the worker:<pre>
603: var nextName = 0;
1.36 ihickson 604: function getNextName() {
605: // this could use more friendly names
606: // but for now just return a number
607: return nextName++;
608: }
609:
610: var map = [
611: [0, 0, 0, 0, 0, 0, 0],
612: [1, 1, 0, 1, 0, 1, 1],
613: [0, 1, 0, 1, 0, 0, 0],
614: [0, 1, 0, 1, 0, 1, 1],
615: [0, 0, 0, 1, 0, 0, 0],
616: [1, 0, 0, 1, 1, 1, 1],
617: [1, 1, 0, 1, 1, 0, 1],
618: ];
619:
620: function wrapX(x) {
621: if (x < 0) return wrapX(x + map[0].length);
1.81 ihickson 622: if (x >= map[0].length) return wrapX(x - map[0].length);
1.36 ihickson 623: return x;
624: }
625:
626: function wrapY(y) {
627: if (y < 0) return wrapY(y + map.length);
1.81 ihickson 628: if (y >= map[0].length) return wrapY(y - map.length);
1.36 ihickson 629: return y;
630: }
631:
1.50 ihickson 632: function sendMapData(callback) {
1.36 ihickson 633: var data = '';
634: for (var y = viewer.y-1; y <= viewer.y+1; y += 1) {
635: for (var x = viewer.x-1; x <= viewer.x+1; x += 1) {
636: if (data != '')
637: data += ',';
638: data += map[y][x];
639: }
640: }
1.50 ihickson 641: callback('map ' + data);
1.36 ihickson 642: }
643:
644: var viewers = {};
645: onconnect = function (event) {
1.84 ihickson 646: event.ports[0]._name = getNextName();
647: event.ports[0]._data = { port: event.port, x: 0, y: 0, };
648: viewers[event.ports[0]._name] = event.port._data;
649: event.ports[0].postMessage('cfg ' + name);
650: event.ports[0].onmessage = getMessage;
651: sendMapData(event.ports[0].postMessage);
1.36 ihickson 652: };
653:
654: function getMessage(event) {
1.54 ihickson 655: switch (event.data.substr(0, 4)) {
1.36 ihickson 656: case 'mov ':
1.54 ihickson 657: var direction = event.data.substr(4);
1.36 ihickson 658: var dx = 0;
659: var dy = 0;
660: switch (direction) {
661: case 'up': dy = -1; break;
662: case 'down': dy = 1; break;
663: case 'left': dx = -1; break;
664: case 'right': dx = 1; break;
665: }
666: event.target._data.x = wrapX(event.target._data.x + dx);
667: event.target._data.y = wrapY(event.target._data.y + dy);
1.50 ihickson 668: sendMapData(event.target.postMessage);
1.36 ihickson 669: break;
670: case 'set ':
1.54 ihickson 671: var value = event.data.substr(4);
1.36 ihickson 672: map[event.target._data.y][event.target._data.x] = value;
673: for (var viewer in viewers)
1.50 ihickson 674: sendMapData(viewers[viewer].port.postMessage);
1.36 ihickson 675: break;
676: case 'txt ':
677: var name = event.target._name;
1.54 ihickson 678: var message = event.data.substr(4);
1.36 ihickson 679: for (var viewer in viewers)
680: viewers[viewer].port.postMessage('txt ' + name + ' ' + message);
681: break;
682: case 'msg ':
683: var party1 = event._data;
1.54 ihickson 684: var party2 = viewers[event.data.substr(4).split(' ', 1)];
1.36 ihickson 685: if (party2) {
686: var channel = new MessageChannel();
1.84 ihickson 687: party1.port.postMessage('msg ' + party2.name, [channel.port1]);
688: party2.port.postMessage('msg ' + party1.name, [channel.port2]);
1.36 ihickson 689: }
690: break;
691: }
1.155 ihickson 692: }</pre><p><strong>Connecting to multiple pages</strong>. The script uses
1.115 ihickson 693: the <code title="handler-SharedWorkerGlobalScope-onconnect"><a href="#handler-sharedworkerglobalscope-onconnect">onconnect</a></code>
1.155 ihickson 694: event listener to listen for multiple connections.<p><strong>Direct channels</strong>. When the worker receives a
1.81 ihickson 695: "msg" message from one viewer naming another viewer, it sets up a
696: direct connection between the two, so that the two viewers can
697: communicate directly without the worker having to proxy all the
1.155 ihickson 698: messages.<p><a href="http://www.whatwg.org/demos/workers/multiviewer/page.html">View this example online</a>.<h4 id="delegation"><span class="secno">1.2.5 </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 699: performance is to split computationally expensive tasks amongst
700: multiple workers. In this example, a computationally expensive task
701: that is to be performed for every number from 1 to 10,000,000 is
1.155 ihickson 702: farmed out to ten subworkers.<p>The main page is as follows, it just reports the result:<pre><!DOCTYPE HTML>
1.81 ihickson 703: <html>
704: <head>
705: <title>Worker example: One-core computation</title>
706: </head>
707: <body>
708: <p>The highest prime number discovered so far is: <output id="result"></output></p>
709: <script>
1.50 ihickson 710: var worker = new Worker('worker.js');
711: worker.onmessage = function (event) {
1.54 ihickson 712: document.getElementById('result').textContent = event.data;
1.40 ihickson 713: };
1.81 ihickson 714: </script>
715: </body>
1.155 ihickson 716: </html></pre><p>The worker itself is as follows:<pre>// settings
1.40 ihickson 717: var num_workers = 10;
718: var items_per_worker = 1000000;
719:
720: // start the workers
721: var result = 0;
722: var pending_workers = num_workers;
723: for (var i = 0; i < num_workers; i += 1) {
1.50 ihickson 724: var worker = new Worker('core.js');
725: worker.postMessage(i * items_per_worker);
726: worker.postMessage((i+1) * items_per_worker);
727: worker.onmessage = storeResult;
1.40 ihickson 728: }
729:
730: // handle the results
731: function storeResult(event) {
1.54 ihickson 732: result += 1*event.data;
1.40 ihickson 733: pending_workers -= 1;
734: if (pending_workers <= 0)
1.50 ihickson 735: postMessage(result); // finished!
1.155 ihickson 736: }</pre><p>It consists of a loop to start the subworkers, and then a handler
737: that waits for all the subworkers to respond.<p>The subworkers are implemented as follows:<pre>var start;
1.41 ihickson 738: onmessage = getStart;
1.40 ihickson 739: function getStart(event) {
1.54 ihickson 740: start = 1*event.data;
1.40 ihickson 741: onmessage = getEnd;
742: }
743:
744: var end;
745: function getEnd(event) {
1.54 ihickson 746: end = 1*event.data;
1.40 ihickson 747: onmessage = null;
1.66 ihickson 748: work();
1.40 ihickson 749: }
750:
1.66 ihickson 751: function work() {
1.40 ihickson 752: var result = 0;
753: for (var i = start; i < end; i += 1) {
754: // perform some complex calculation here
755: result += 1;
756: }
1.50 ihickson 757: postMessage(result);
758: close();
1.155 ihickson 759: }</pre><p>They receive two numbers in two events, perform the computation
1.81 ihickson 760: for the range of numbers thus specified, and then report the result
1.155 ihickson 761: back to the parent.<p><a href="http://www.whatwg.org/demos/workers/multicore/page.html">View this example online</a>.<h4 id="providing-libraries"><span class="secno">1.2.6 </span>Providing libraries</h4><p><i>This section is non-normative.</i><p>Suppose that a cryptography library is made available that
762: provides three tasks:<dl><dt>Generate a public/private key pair</dt>
1.81 ihickson 763:
764: <dd>Takes a port, on which it will send two messages, first the
765: public key and then the private key.</dd>
766:
767: <dt>Given a plaintext and a public key, return the corresponding cyphertext</dt>
768:
769: <dd>Takes a port, to which any number of messages can be sent, the
770: first giving the public key, and the remainder giving the
771: plaintext, each of which is encrypted and then sent on that same
772: channel as the cyphertext. The user can close the port when it is
773: done encrypting content.</dd>
774:
775: <dt>Given a cyphertext and a private key, return the corresponding plaintext</dt>
776:
777: <dd>Takes a port, to which any number of messages can be sent, the
778: first giving the private key, and the remainder giving the
779: cyphertext, each of which is decrypted and then sent on that same
780: channel as the plaintext. The user can close the port when it is
781: done decrypting content.</dd>
1.49 ihickson 782:
1.155 ihickson 783: </dl><p>The library itself is as follows:<pre>function handleMessage(e) {
1.54 ihickson 784: if (e.data == "genkeys")
1.84 ihickson 785: genkeys(e.ports[0]);
1.54 ihickson 786: else if (e.data == "encrypt")
1.84 ihickson 787: encrypt(e.ports[0]);
1.54 ihickson 788: else if (e.data == "decrypt")
1.84 ihickson 789: decrypt(e.ports[0]);
1.49 ihickson 790: }
791:
792: function genkeys(p) {
793: var keys = _generateKeyPair();
794: p.postMessage(keys[0]);
795: p.postMessage(keys[1]);
796: }
797:
798: function encrypt(p) {
799: var key, state = 0;
800: p.onmessage = function (e) {
801: if (state == 0) {
1.54 ihickson 802: key = e.data;
1.49 ihickson 803: state = 1;
804: } else {
1.54 ihickson 805: p.postMessage(_encrypt(key, e.data));
1.49 ihickson 806: }
807: };
808: }
809:
810: function decrypt(p) {
811: var key, state = 0;
812: p.onmessage = function (e) {
813: if (state == 0) {
1.54 ihickson 814: key = e.data;
1.49 ihickson 815: state = 1;
816: } else {
1.54 ihickson 817: p.postMessage(_decrypt(key, e.data));
1.49 ihickson 818: }
819: };
820: }
821:
1.50 ihickson 822: // support being used as a shared worker as well as a dedicated worker
823: if (this.onmessage) // dedicated worker
824: onmessage = handleMessage;
825: else // shared worker
826: onconnect = function (e) { e.port.onmessage = handleMessage; }
1.49 ihickson 827:
828:
829: // the "crypto" functions:
830:
831: function _generateKeyPair() {
832: return [Math.random(), Math.random()];
833: }
834:
835: function _encrypt(k, s) {
836: return 'encrypted-' + k + ' ' + s;
837: }
838:
839: function _decrypt(k, s) {
840: return s.substr(s.indexOf(' ')+1);
1.155 ihickson 841: }</pre><p>Note that the crypto functions here are just stubs and don't do
842: real cryptography.<p>This library could be used as follows:<pre><!DOCTYPE HTML>
1.81 ihickson 843: <html>
844: <head>
845: <title>Worker example: Crypto library</title>
846: <script>
1.50 ihickson 847: var crytoLib = new Worker('libcrypto-v1.js'); // or could use 'libcrypto-v2.js'
1.49 ihickson 848: function getKeys() {
849: var state = 0;
1.50 ihickson 850: cryptoLib.startConversation("genkeys").onmessage = function (e) {
1.49 ihickson 851: if (state == 0)
1.54 ihickson 852: document.getElementById('public').value = e.data;
1.49 ihickson 853: else if (state == 1)
1.54 ihickson 854: document.getElementById('private').value = e.data;
1.49 ihickson 855: state += 1;
856: };
857: }
858: function enc() {
1.50 ihickson 859: var port = cryptoLib.startConversation("encrypt");
860: port.postMessage(document.getElementById('public').value);
861: port.postMessage(document.getElementById('input').value);
862: port.onmessage = function (e) {
1.54 ihickson 863: document.getElementById('input').value = e.data;
1.50 ihickson 864: port.close();
1.49 ihickson 865: };
866: }
867: function dec() {
1.50 ihickson 868: var port = cryptoLib.startConversation("decrypt");
869: port.postMessage(document.getElementById('private').value);
870: port.postMessage(document.getElementById('input').value);
871: port.onmessage = function (e) {
1.54 ihickson 872: document.getElementById('input').value = e.data;
1.50 ihickson 873: port.close();
1.49 ihickson 874: };
875: }
1.81 ihickson 876: </script>
877: <style>
1.49 ihickson 878: textarea { display: block; }
1.81 ihickson 879: </style>
880: </head>
881: <body onload="getKeys()">
882: <fieldset>
883: <legend>Keys</legend>
884: <p><label>Public Key: <textarea id="public"></textarea></label></p>
885: <p><label>Private Key: <textarea id="private"></textarea></label></p>
886: </fieldset>
887: <p><label>Input: <textarea id="input"></textarea></label></p>
888: <p><button onclick="enc()">Encrypt</button> <button onclick="dec()">Decrypt</button></p>
889: </body>
1.155 ihickson 890: </html></pre><p>A later version of the API, though, might want to offload all the
891: crypto work onto subworkers. This could be done as follows:<pre>function handleMessage(e) {
1.54 ihickson 892: if (e.data == "genkeys")
1.84 ihickson 893: genkeys(e.ports[0]);
1.54 ihickson 894: else if (e.data == "encrypt")
1.84 ihickson 895: encrypt(e.ports[0]);
1.54 ihickson 896: else if (e.data == "decrypt")
1.84 ihickson 897: decrypt(e.ports[0]);
1.49 ihickson 898: }
899:
900: function genkeys(p) {
1.50 ihickson 901: var generator = new Worker('libcrypto-v2-generator.js');
1.84 ihickson 902: generator.postMessage('', [p]);
1.49 ihickson 903: }
904:
905: function encrypt(p) {
906: p.onmessage = function (e) {
1.54 ihickson 907: var key = e.data;
1.50 ihickson 908: var encryptor = new Worker('libcrypto-v2-encryptor.js');
1.84 ihickson 909: encryptor.postMessage(key, [p]);
1.49 ihickson 910: };
911: }
912:
913: function encrypt(p) {
914: p.onmessage = function (e) {
1.54 ihickson 915: var key = e.data;
1.50 ihickson 916: var decryptor = new Worker('libcrypto-v2-decryptor.js');
1.84 ihickson 917: decryptor.postMessage(key, [p]);
1.49 ihickson 918: };
919: }
920:
1.50 ihickson 921: // support being used as a shared worker as well as a dedicated worker
922: if (this.onmessage) // dedicated worker
923: onmessage = handleMessage;
924: else // shared worker
1.84 ihickson 925: onconnect = function (e) { e.ports[0].onmessage = handleMessage };
1.155 ihickson 926: </pre><p>The little subworkers would then be as follows.<p>For generating key pairs:<pre>onmessage = function (e) {
1.50 ihickson 927: var k = _generateKeyPair();
1.84 ihickson 928: e.ports[0].postMessage(k[0]);
929: e.ports[0].postMessage(k[1]);
1.49 ihickson 930: close();
931: }
1.50 ihickson 932:
933: function _generateKeyPair() {
934: return [Math.random(), Math.random()];
1.155 ihickson 935: }</pre><p>For encrypting:<pre>onmessage = function (e) {
1.54 ihickson 936: var key = e.data;
1.84 ihickson 937: e.ports[0].onmessage = function (e) {
1.54 ihickson 938: var s = e.data;
1.50 ihickson 939: postMessage(_encrypt(key, s));
1.49 ihickson 940: }
1.50 ihickson 941: }
942:
943: function _encrypt(k, s) {
944: return 'encrypted-' + k + ' ' + s;
1.155 ihickson 945: }</pre><p>For decrypting:<pre>onmessage = function (e) {
1.54 ihickson 946: var key = e.data;
1.84 ihickson 947: e.ports[0].onmessage = function (e) {
1.54 ihickson 948: var s = e.data;
1.50 ihickson 949: postMessage(_decrypt(key, s));
1.49 ihickson 950: }
1.50 ihickson 951: }
952:
953: function _decrypt(k, s) {
954: return s.substr(s.indexOf(' ')+1);
1.155 ihickson 955: }</pre><p>Notice how the users of the API don't have to even know that this
956: is happening — the API hasn't changed; the library can
1.81 ihickson 957: delegate to subworkers without changing its API, even though it is
1.155 ihickson 958: accepting data using message channels.<p><a href="http://www.whatwg.org/demos/workers/crypto/page.html">View this example online</a>.<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 959: non-normative, as are all sections explicitly marked non-normative.
1.155 ihickson 960: Everything else in this specification is normative.<p>The key words "MUST", "MUST NOT", "REQUIRED", <!--"SHALL", "SHALL
1.81 ihickson 961: NOT",--> "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
962: "OPTIONAL" in the normative parts of this document are to be
963: interpreted as described in RFC2119. For readability, these words do
1.155 ihickson 964: 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 965: (such as "strip any leading space characters" or "return false and
966: abort these steps") are to be interpreted with the meaning of the
967: key word ("must", "should", "may", etc) used in introducing the
1.155 ihickson 968: algorithm.<p>Some conformance requirements are phrased as requirements on
1.81 ihickson 969: attributes, methods or objects. Such requirements are to be
1.155 ihickson 970: interpreted as requirements on user agents.<p>Conformance requirements phrased as algorithms or specific steps
1.81 ihickson 971: may be implemented in any manner, so long as the end result is
972: equivalent. (In particular, the algorithms defined in this
973: specification are intended to be easy to follow, and not intended to
1.155 ihickson 974: be performant.)<p>The only conformance class defined by this specification is user
975: agents.<p>User agents may impose implementation-specific limits on
1.81 ihickson 976: otherwise unconstrained inputs, e.g. to prevent denial of service
977: attacks, to guard against running out of memory, or to work around
1.155 ihickson 978: platform-specific limitations.<h3 id="dependencies"><span class="secno">2.1 </span>Dependencies</h3><p>This specification relies on several other underlying
979: specifications.<dl><dt>HTML5</dt>
1.49 ihickson 980:
1.81 ihickson 981: <dd>
1.49 ihickson 982:
1.81 ihickson 983: <p>Many fundamental concepts from HTML5 are used by this
1.152 ihickson 984: specification. <a href="#refsHTML5">[HTML5]</a></p>
1.49 ihickson 985:
1.81 ihickson 986: </dd>
1.1 ihickson 987:
1.81 ihickson 988: <dt>WebIDL</dt>
1.1 ihickson 989:
990: <dd>
991:
1.81 ihickson 992: <p>The IDL blocks in this specification use the semantics of the
1.153 ihickson 993: WebIDL specification. <a href="#refsWEBIDL">[WEBIDL]</a></p>
1.1 ihickson 994:
1.81 ihickson 995: </dd>
1.1 ihickson 996:
1.155 ihickson 997: </dl><h2 id="terminology"><span class="secno">3 </span>Terminology</h2><p>The construction "a <code title="">Foo</code> object", where
1.81 ihickson 998: <code title="">Foo</code> is actually an interface, is sometimes
999: used instead of the more accurate "an object implementing the
1.155 ihickson 1000: interface <code title="">Foo</code>".<p>The term DOM is used to refer to the API set made available to
1.81 ihickson 1001: scripts in Web applications, and does not necessarily imply the
1002: existence of an actual <code>Document</code> object or of any other
1003: <code>Node</code> objects as defined in the DOM Core
1.171 ihickson 1004: specifications. <a href="#refsDOMCORE">[DOMCORE]</a><p>An IDL attribute is said to be <em>getting</em> when its value is
1.81 ihickson 1005: being retrieved (e.g. by author script), and is said to be
1.155 ihickson 1006: <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 1007: the official term ECMAScript, since the term JavaScript is more
1.155 ihickson 1008: 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 1009: workers. Dedicated workers, once created, and are linked to their
1010: creator; but message ports can be used to communicate from a
1011: dedicated worker to multiple other browsing contexts or
1012: workers. Shared workers, on the other hand, are named, and once
1013: created any script running in the same <span>origin</span> can
1.155 ihickson 1014: obtain a reference to that worker and communicate with it.<h3 id="the-global-scope"><span class="secno">4.1 </span>The global scope</h3><p>The global scope is the "inside" of a worker.<h4 id="the-workerglobalscope-abstract-interface"><span class="secno">4.1.1 </span>The <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> abstract interface</h4><pre class="idl">interface <dfn id="workerglobalscope">WorkerGlobalScope</dfn> {
1.115 ihickson 1015: readonly attribute <a href="#workerglobalscope">WorkerGlobalScope</a> <a href="#dom-workerglobalscope-self" title="dom-WorkerGlobalScope-self">self</a>;
1016: readonly attribute <a href="#workerlocation">WorkerLocation</a> <a href="#dom-workerglobalscope-location" title="dom-WorkerGlobalScope-location">location</a>;
1017:
1018: void <a href="#dom-workerglobalscope-close" title="dom-WorkerGlobalScope-close">close</a>();
1.144 ihickson 1019: <!-- v2-onclose attribute <span>Function</span> <span title="handler-WorkerGlobalScope-onclose">onclose</span>;
1020: --> attribute <span>Function</span> <a href="#handler-workerglobalscope-onerror" title="handler-WorkerGlobalScope-onerror">onerror</a>;
1.150 ihickson 1021: };
1.172 ihickson 1022: <a href="#workerglobalscope">WorkerGlobalScope</a> implements <a href="#workerutils">WorkerUtils</a>;
1023: <a href="#workerglobalscope">WorkerGlobalScope</a> implements <span>EventTarget</span>;</pre><p>The <dfn id="dom-workerglobalscope-self" title="dom-WorkerGlobalScope-self"><code>self</code></dfn> attribute
1.155 ihickson 1024: 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 1025: attribute must return the <code><a href="#workerlocation">WorkerLocation</a></code> object created
1026: for the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object when the worker was
1.81 ihickson 1027: created. It represents the <span>absolute URL</span> of the script
1.155 ihickson 1028: 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 1029: method on a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, the user agent
1.155 ihickson 1030: must run the following steps (atomically):<ol><li><p>Discard any <span title="concept-task">tasks</span> that
1.123 ihickson 1031: have been added to the <span>event loop</span>'s <span title="task
1032: queue">task queues</span>.</p>
1033:
1034: <!-- v2-onclose
1035: <li><p><span>Queue a task</span> to <span>fire a simple
1.115 ihickson 1036: event</span> called <code title="event-close">close</code> at the
1.123 ihickson 1037: <code>WorkerGlobalScope</code> object.</p></li>
1038: -->
1.81 ihickson 1039:
1.115 ihickson 1040: <li><p>Set the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object's
1041: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag to
1.123 ihickson 1042: true. (This prevents any further tasks from being queued.)</li>
1.81 ihickson 1043:
1.124 ihickson 1044: <li><p>Disentangle all the ports in the list of <a href="#the-worker-s-ports">the worker's
1.123 ihickson 1045: ports</a>.</li>
1.81 ihickson 1046:
1.177 ihickson 1047: </ol><p>The following are the <span>event handlers</span> (and their
1048: corresponding <span title="event handler event type">event handler
1049: event types</span>) that must be supported, as IDL attributes, by
1050: objects implementing the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1051: interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1052: <tbody><!-- v2-onclose <tr><td><dfn title="handler-WorkerGlobalScope-onclose"><code>onclose</code></dfn> <td> <code title="event-close">close</code> --><tr><td><dfn id="handler-workerglobalscope-onerror" title="handler-WorkerGlobalScope-onerror"><code>onerror</code></dfn> <td> <code title="event-error">error</code>
1053: </table><h4 id="dedicated-workers-and-the-dedicatedworkerglobalscope-interface"><span class="secno">4.1.2 </span>Dedicated workers and the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> interface</h4><pre class="idl">[Supplemental, NoInterfaceObject]
1.150 ihickson 1054: interface <dfn id="dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</dfn> : <a href="#workerglobalscope">WorkerGlobalScope</a> {
1.174 ihickson 1055: void <a href="#dom-dedicatedworkerglobalscope-postmessage" title="dom-DedicatedWorkerGlobalScope-postMessage">postMessage</a>(in any message, in optional <span>MessagePortArray</span> ports);<!--
1.77 ihickson 1056: <span>MessagePort</span> <span title="dom-DedicatedWorkerGlobalScope-startConversation">startConversation</span>(in any message);-->
1.144 ihickson 1057: attribute <span>Function</span> <a href="#handler-dedicatedworkerglobalscope-onmessage" title="handler-DedicatedWorkerGlobalScope-onmessage">onmessage</a>;
1.155 ihickson 1058: };</pre><p><code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> objects act as if they
1.81 ihickson 1059: had an implicit <code>MessagePort</code> associated with them. This
1060: port is part of a channel that is set up when the worker is created,
1061: but it is not exposed. This object must never be garbage collected
1.155 ihickson 1062: before the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object.<p>All messages received by that port must immediately be retargeted
1063: 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><!--
1.64 ihickson 1064: and <dfn
1065: title="dom-DedicatedWorkerGlobalScope-startConversation"><code>startConversation()</code></dfn>-->
1.81 ihickson 1066: method<!--s (startConversation)--> on
1.115 ihickson 1067: <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> objects must act as if, when
1.81 ihickson 1068: invoked, it<!--/they (startConversation)--> immediately invoked the
1069: method of the same name on the port, with the same arguments, and
1.177 ihickson 1070: returned the same return value.<p>The following are the <span>event handlers</span> (and their
1071: corresponding <span title="event handler event type">event handler
1072: event types</span>) that must be supported, as IDL attributes, by
1073: objects implementing the <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
1074: interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1075: <tbody><tr><td><dfn id="handler-dedicatedworkerglobalscope-onmessage" title="handler-DedicatedWorkerGlobalScope-onmessage"><code>onmessage</code></dfn> <td> <code title="event-message">message</code>
1076: </table><p>For the purposes of the <span>offline application cache</span>
1.101 ihickson 1077: networking model, a dedicated worker is an extension of the
1.155 ihickson 1078: <span>cache host</span> from which it was created.<h4 id="shared-workers-and-the-sharedworkerglobalscope-inteface"><span class="secno">4.1.3 </span>Shared workers and the <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> inteface</h4><pre class="idl">[Supplemental, NoInterfaceObject]
1.150 ihickson 1079: interface <dfn id="sharedworkerglobalscope">SharedWorkerGlobalScope</dfn> : <a href="#workerglobalscope">WorkerGlobalScope</a> {
1.115 ihickson 1080: readonly attribute DOMString <a href="#dom-sharedworkerglobalscope-name" title="dom-SharedWorkerGlobalScope-name">name</a>;
1081: readonly attribute <span>ApplicationCache</span> <a href="#dom-sharedworkerglobalscope-applicationcache" title="dom-SharedWorkerGlobalScope-applicationCache">applicationCache</a>;
1.144 ihickson 1082: attribute <span>Function</span> <a href="#handler-sharedworkerglobalscope-onconnect" title="handler-SharedWorkerGlobalScope-onconnect">onconnect</a>;
1.155 ihickson 1083: };</pre><p>Shared workers receive message ports through <code title="event-WorkerGlobalScope-connect">connect</code> events on
1084: their global object for each connection.<p>The <dfn id="dom-sharedworkerglobalscope-name" title="dom-SharedWorkerGlobalScope-name"><code>name</code></dfn>
1.81 ihickson 1085: attribute must return the value it was assigned when the
1.115 ihickson 1086: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object was created by the
1087: "<a href="#run-a-worker">run a worker</a>" algorithm. Its value represents the name
1.81 ihickson 1088: that can be used to obtain a reference to the worker using the
1.177 ihickson 1089: <code><a href="#sharedworker">SharedWorker</a></code> constructor.<p>The following are the <span>event handlers</span> (and their
1090: corresponding <span title="event handler event type">event handler
1091: event types</span>) that must be supported, as IDL attributes, by
1092: objects implementing the <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1093: interface:<table><thead><tr><th><span title="event handlers">Event handler</span> <th><span>Event handler event type</span>
1.155 ihickson 1094: <tbody><tr><td><dfn id="handler-sharedworkerglobalscope-onconnect" title="handler-SharedWorkerGlobalScope-onconnect"><code>onconnect</code></dfn> <td> <code title="event-connect">connect</code>
1095: </table><p>For the purposes of the <span>offline application cache</span>
1.101 ihickson 1096: networking model, a shared worker is its own <span>cache
1.115 ihickson 1097: host</span>. The <a href="#run-a-worker">run a worker</a> algorithm takes care of
1.155 ihickson 1098: associating the worker with an <span>application cache</span>.<p class="note">The <dfn id="dom-sharedworkerglobalscope-applicationcache" title="dom-SharedWorkerGlobalScope-applicationCache"><code>applicationCache</code></dfn>
1.123 ihickson 1099: attribute returns the <code>ApplicationCache</code> object for the
1.101 ihickson 1100: worker.</p><!-- normative conf criteria is in the appcache section
1.160 ihickson 1101: --><h3 id="origins-of-workers"><span class="secno">4.2 </span>Origins of workers</h3><p>Both the <span>origin</span> and <span>effective script
1.81 ihickson 1102: origin</span> of scripts running in workers are the
1103: <span>origin</span> of the <span>absolute URL</span> given in that
1.115 ihickson 1104: the worker's <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1.155 ihickson 1105: represents.<h3 id="decoding-scripts"><span class="secno">4.3 </span>Decoding scripts</h3><p>When a user agent is to <dfn id="decode-a-script-resource">decode a script resource</dfn> to
1106: obtain its source in Unicode, it must run the following steps:<ol><li>
1.85 ihickson 1107:
1108: <p>Let <var title="">character encoding</var> be <i title="">unknown</i>.</p>
1109:
1110: </li>
1111:
1112: <li>
1113:
1114: <p>For each of the rows in the following table, starting with the
1115: first one and going down, if the resource has as many or more
1116: bytes available than the number of bytes in the first column, and
1117: the first bytes of the resource match the bytes given in the first
1118: column, then let <var title="">character encoding</var> be the
1119: encoding given in the cell in the second column of that row:</p>
1120:
1121: <!-- this table is present in several forms in this file; keep them in sync -->
1.155 ihickson 1122: <table><thead><tr><th>Bytes in Hexadecimal
1.85 ihickson 1123: <th>Encoding
1.155 ihickson 1124: <tbody><!-- nobody uses this
1.85 ihickson 1125: <tr>
1126: <td>00 00 FE FF
1127: <td>UTF-32BE
1128: <tr>
1129: <td>FF FE 00 00
1130: <td>UTF-32LE
1.155 ihickson 1131: --><tr><td>FE FF
1.85 ihickson 1132: <td>UTF-16BE
1.155 ihickson 1133: <tr><td>FF FE
1.85 ihickson 1134: <td>UTF-16LE
1.155 ihickson 1135: <tr><td>EF BB BF
1.85 ihickson 1136: <td>UTF-8
1137: <!-- nobody uses this
1138: <tr>
1139: <td>DD 73 66 73
1140: <td>UTF-EBCDIC
1141: -->
1.155 ihickson 1142: </table><p class="note">This step looks for Unicode Byte Order Marks
1.85 ihickson 1143: (BOMs).</p>
1144:
1145: </li>
1146:
1147: <li>
1148:
1149: <p>If <var title="">character encoding</var> is still <i title="">unknown</i>, apply the <span>algorithm for extracting an
1.115 ihickson 1150: encoding from a Content-Type</span> to the resource's <span title="Content-Type">Content Type metadata</span>; if this returns
1.85 ihickson 1151: an encoding, and the user agent supports that encoding, then let
1152: <var title="">character encoding</var> be that encoding.</p>
1153:
1154: </li>
1155:
1156: <li>
1157:
1158: <p>If <var title="">character encoding</var> is still <i title="">unknown</i>, then let <var title="">character
1159: encoding</var> be UTF-8.</p>
1160:
1161: </li>
1162:
1163: <li>
1164:
1165: <p>Convert the resource to Unicode using the character encoding
1166: given by <var title="">character encoding</var>.</p>
1167:
1168: <p>Return the text that is so obtained.</p>
1169:
1170: </li>
1171:
1.155 ihickson 1172: </ol><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 1173: loop</span> distinct from those defined for <span title="unit of
1174: related similar-origin browsing contexts">units of related
1175: similar-origin browsing contexts</span>. This <span>event
1176: loop</span> has no associated <span>browsing context</span>, and its
1177: <span title="task queue">task queues</span> only have events,
1178: callbacks, and networking activity as <span title="concept-task">tasks</span>. The processing model of these
1179: <span title="event loop">event loops</span> is defined below in the
1.155 ihickson 1180: <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 1181: initially be false, but which can get set to true by the algorithms
1.155 ihickson 1182: 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 1183: true, the <span>event loop</span>'s <span title="task queue">task
1.115 ihickson 1184: queues</span> must discard any further <span title="concept-task">tasks</span> that would be added to them (tasks
1.175 ihickson 1185: already on the queue are unaffected except where otherwise
1.115 ihickson 1186: specified). Effectively, once the <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is true,
1.81 ihickson 1187: timers stop firing, notifications for all pending asynchronous
1.155 ihickson 1188: 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
1189: <code>MessagePort</code> objects.<p>Each <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> <var title="">worker global
1.124 ihickson 1190: scope</var> has a list of <dfn id="the-worker-s-ports">the worker's ports</dfn>, which
1.81 ihickson 1191: consists of all the <code>MessagePort</code> objects that are
1192: entangled with another port and that have one (but only one) port
1193: owned by <var title="">worker global scope</var>. This list includes
1194: <!--all the <code>MessagePort</code> objects that are in events
1.68 ihickson 1195: pending in the <span>event loop</span>, as well as (commented out
1196: because in practice it makes no difference either way as far as I
1197: can tell, and it would be hard to strictly implement since these
1.81 ihickson 1198: ports might not yet be across the thread boundary)--> the implicit
1.155 ihickson 1199: <code>MessagePort</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 1200: worker's workers</dfn>. Initially this list is empty; it is
1.155 ihickson 1201: 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 1202: <dfn id="the-worker-s-documents">the worker's <code>Document</code>s</dfn>. Initially this list
1.155 ihickson 1203: 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 1204: worker's <code>Document</code>s</dfn>, the user agent must, for each
1.124 ihickson 1205: worker in the list of <a href="#the-worker-s-workers">the worker's workers</a> whose list
1206: of <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a> does not contain
1207: <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 1208: documents">add <var title="">d</var> to <var title="">q</var>'s
1209: <code>WorkerGlobalScope</code> owner's list of <span>the worker's
1.155 ihickson 1210: <code>Document</code>s</span></a>.</p><!-- suggestions welcome
1211: on making this sentence into understandable English --><p>Whenever a <code>Document</code> object is <span title="discard a
1.123 ihickson 1212: Document">discarded</span>, it must be removed from the list of
1213: <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a> of each worker
1.155 ihickson 1214: whose list contains that <code>Document</code>.<p>Given a <span>script's global scope</span> <var title="">o</var>
1.123 ihickson 1215: when creating or obtaining a worker, the <dfn id="list-of-relevant-document-objects-to-add">list of relevant
1216: <code>Document</code> objects to add</dfn> depends on the type of
1217: <var title="">o</var>. If <var title="">o</var> is a
1218: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object (i.e. if we are creating a
1219: nested worker), then the relevant <code>Document</code>s are the
1220: <code>Document</code>s that are in <var title="">o</var>'s own list
1221: 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
1222: <code>Document</code> is just the <code>Document</code> that is the
1.155 ihickson 1223: <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 1224: list of <a href="#the-worker-s-documents">the worker's <code>Document</code>s</a> is not
1.155 ihickson 1225: empty.<p>A worker is said to be a <dfn id="protected-worker">protected worker</dfn> if it is a
1.123 ihickson 1226: <a href="#permissible-worker">permissible worker</a> and either it has outstanding
1227: timers, database transactions, or network connections, or its list
1.124 ihickson 1228: of <a href="#the-worker-s-ports">the worker's ports</a> is not empty, or its
1.123 ihickson 1229: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> is actually a
1230: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object (i.e. the worker is a
1.155 ihickson 1231: shared worker).<p>A worker is said to be an <dfn id="active-needed-worker">active needed worker</dfn> if any
1.123 ihickson 1232: of the <code>Document</code> objects in <a href="#the-worker-s-documents">the worker's
1.155 ihickson 1233: <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 1234: not an <a href="#active-needed-worker">active needed worker</a> but it is a
1.155 ihickson 1235: <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
1.176 ihickson 1236: <span>URL</span> <var title="">url</var>, a browsing context <var title="">owner browsing context</var>, an origin <var title="">owner
1237: origin</var>, and with global scope <var title="">worker global
1238: scope</var>, it must run the following steps:<ol><li>
1.81 ihickson 1239:
1240: <p>Create a completely separate and parallel execution environment
1241: (i.e. a separate thread or process or equivalent construct), and
1.106 ihickson 1242: run the rest of these steps asynchronously in that context.</p>
1.81 ihickson 1243:
1244: </li>
1.4 ihickson 1245:
1.101 ihickson 1246: <li><p>If <var title="">worker global scope</var> is actually a
1.115 ihickson 1247: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object (i.e. the worker is a
1.101 ihickson 1248: shared worker), and there are any <span title="relevant application
1249: cache">relevant application caches</span> that are identified by a
1250: 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 1251: their entries, <em>not</em> excluding entries marked as <span title="concept-appcache-foreign">foreign</span>, then associate the
1252: <var title="">worker global scope</var> with the <span title="concept-appcache-selection">most appropriate application
1.101 ihickson 1253: cache</span> of those that match.</li>
1254:
1.4 ihickson 1255: <li>
1.52 ihickson 1256:
1.176 ihickson 1257: <p>Attempt to <span>fetch</span> the resource identified by <var title="">url</var>, from the <var title="">owner origin</var>.</p>
1258: <!-- not http-origin privacy sensitive -->
1.81 ihickson 1259:
1.129 ihickson 1260: <p>If the attempt fails, or if the attempt involves any redirects
1261: to URIs that do not have the <span>same origin</span> as <var title="">url</var> (even if the final URI is at the <span>same
1262: origin</span> as the original <var title="">url</var>), then for
1263: each <code><a href="#worker">Worker</a></code> or <code><a href="#sharedworker">SharedWorker</a></code> object
1264: associated with <var title="">worker global scope</var>,
1265: <span>queue a task</span> to <span>fire a simple event</span>
1266: called <code title="event-error">error</code> at that
1267: object. Abort these steps.</p>
1.7 ihickson 1268:
1.115 ihickson 1269: <p>If the attempt succeeds, then <a href="#decode-a-script-resource" title="decode a script
1.85 ihickson 1270: resource">decode the script resource</a> to obtain its <var title="">source</var>.</p>
1.81 ihickson 1271:
1.68 ihickson 1272: <p>Let <var title="">language</var> be JavaScript.</p>
1.7 ihickson 1273:
1.115 ihickson 1274: <p class="note">As with <code>script</code> elements, the MIME
1.81 ihickson 1275: type of the script is ignored. Unlike with <code>script</code>
1276: elements, there is no way to override the type. It's always
1.170 ihickson 1277: assumed to be JavaScript.</p>
1.81 ihickson 1278:
1279: </li>
1.7 ihickson 1280:
1281: <li>
1.68 ihickson 1282:
1.115 ihickson 1283: <p>A new <span title="concept-script">script</span> is now
1.81 ihickson 1284: created, as follows.</p>
1285:
1286: <p>Create a new <span>script execution environment</span>
1287: set up as appropriate for the scripting language <var title="">language</var>.</p>
1.34 ihickson 1288:
1.68 ihickson 1289: <p>Parse/compile/initialize <var title="">source</var> using that
1.81 ihickson 1290: <span>script execution environment</span>, as appropriate for <var title="">language</var>, and thus obtain a <span>list of code
1291: entry-points</span>; set the <i>initial code entry-point</i> to
1292: the entry-point for any executable code to be immediately run.</p>
1293:
1294: <p>Set the <span>script's global object</span> to <var title="">worker global scope</var>.</p>
1295:
1296: <p>Set the <span>script's browsing context</span> to <var title="">owner browsing context</var>.</p>
1297:
1.83 ihickson 1298: <p>Set the <span>script's URL character encoding</span> to
1.81 ihickson 1299: UTF-8. (This is just used for encoding non-ASCII characters in the
1300: query component of URLs.)</p>
1.68 ihickson 1301:
1302: <p>Set the <span>script's base URL</span> to <var title="">url</var>.</p>
1.4 ihickson 1303:
1.81 ihickson 1304: </li>
1.4 ihickson 1305:
1306: <li>
1.81 ihickson 1307:
1308: <p><strong>Closing orphan workers</strong>: Start monitoring the
1.125 ihickson 1309: worker such that no sooner than it stops being either a
1310: <a href="#protected-worker">protected worker</a> or a <a href="#suspendable-worker">suspendable
1.123 ihickson 1311: worker</a>, and no later than it stops being a
1312: <a href="#permissible-worker">permissible worker</a>, <var title="">worker global
1313: scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is set
1314: to true<!-- v2-onclose and <span title="queue a task">a task is
1315: queued</span> to <span>fire a simple event</span> called <code
1316: title="event-close">close</code> at <var title="">worker global
1317: scope</var>-->.</p>
1.81 ihickson 1318:
1319: </li>
1.9 ihickson 1320:
1321: <li>
1.7 ihickson 1322:
1.81 ihickson 1323: <p><strong>Suspending workers</strong>: Start monitoring the
1324: worker, such that whenever <var title="">worker global
1.115 ihickson 1325: scope</var>'s <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag is false
1326: and the worker is a <a href="#suspendable-worker">suspendable worker</a>, the user
1.81 ihickson 1327: agent suspends execution of script in that worker until such time
1.115 ihickson 1328: as either the <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag switches
1329: to true or the worker stops being a <a href="#suspendable-worker">suspendable
1.81 ihickson 1330: worker</a>.</p>
1.4 ihickson 1331:
1.81 ihickson 1332: </li>
1.68 ihickson 1333:
1334: <li>
1.4 ihickson 1335:
1.81 ihickson 1336: <p><span title="jump to a code entry-point">Jump</span> to the
1.115 ihickson 1337: <span title="concept-script">script</span>'s <i>initial code
1.81 ihickson 1338: entry-point</i>, and let that run until it either returns, fails
1339: to catch an exception, or gets prematurely aborted by the
1.115 ihickson 1340: "<a href="#kill-a-worker">kill a worker</a>" or "<a href="#terminate-a-worker">terminate a worker</a>"
1.81 ihickson 1341: algorithms defined below.</p>
1342:
1.149 ihickson 1343: <!-- v2-onclose
1344: <p class="note">If the script gets aborted by the "<span>kill a
1345: worker</span>" algorithm, then that same algorithm will cause
1.115 ihickson 1346: there to only be a single <span title="concept-task">task</span>
1.81 ihickson 1347: in the <span>event loop</span> at the next step, namely the task
1.115 ihickson 1348: for the <code title="message-close">close</code> event. The
1.149 ihickson 1349: "<span>terminate a worker</span>" algorithm removes all the
1.81 ihickson 1350: events.</p>
1.149 ihickson 1351: -->
1.4 ihickson 1352:
1.81 ihickson 1353: </li>
1.4 ihickson 1354:
1.95 ihickson 1355: <li><p>If <var title="">worker global scope</var> is actually a
1.115 ihickson 1356: <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object (i.e. the worker is
1.126 ihickson 1357: a dedicated worker), then enable the <span>port message
1358: queue</span> of the worker's implicit port.</li>
1.95 ihickson 1359:
1.4 ihickson 1360: <li>
1.68 ihickson 1361:
1.115 ihickson 1362: <p><i title="">Event loop</i>: Wait until either there is a <span title="concept-task">task</span> in one of the <span>event
1363: 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 1364: to true.</p>
1.43 ihickson 1365:
1.81 ihickson 1366: </li>
1.4 ihickson 1367:
1368: <li>
1369:
1.81 ihickson 1370: <p>Run the oldest task on one of the <span>event loop</span>'s
1371: <span title="task queue">task queues</span>, if any. The user
1372: agent may pick any <span>task queue</span>.</p>
1373:
1.115 ihickson 1374: <p class="note">The handling of events or the execution of
1375: callbacks might get prematurely aborted by the "<a href="#kill-a-worker">kill a
1376: worker</a>" or "<a href="#terminate-a-worker">terminate a worker</a>" algorithms
1.81 ihickson 1377: defined below.</p>
1.8 ihickson 1378:
1.81 ihickson 1379: </li>
1.4 ihickson 1380:
1381: <li>
1382:
1.81 ihickson 1383: <p>Remove the task run in the previous step, if any, from its
1384: <span>task queue</span>.</p>
1.4 ihickson 1385:
1.81 ihickson 1386: </li>
1.4 ihickson 1387:
1388: <li>
1.8 ihickson 1389:
1.81 ihickson 1390: <p>If there are any more events in the <span>event loop</span>'s
1.115 ihickson 1391: <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 1392: to false, then jump back to the step above labeled <i>event
1393: loop</i>.</p>
1.8 ihickson 1394:
1.81 ihickson 1395: </li>
1.8 ihickson 1396:
1397: <li>
1.71 ihickson 1398:
1.123 ihickson 1399: <p>If there are any outstanding transactions that have callbacks
1400: that involve <span title="concept-script">scripts</span> whose
1401: <span title="script's global object">global object</span> is the
1402: <var title="">worker global scope</var>, roll them back (without
1403: invoking any of the callbacks).</p>
1.50 ihickson 1404:
1.123 ihickson 1405: </li>
1406:
1407: <li>
1408:
1409: <p>Empty the <var title="">worker global scope</var>'s <span>list
1410: of active timeouts</span> and its <span>list of active
1411: intervals</span>.</p>
1.50 ihickson 1412:
1.81 ihickson 1413: </li>
1.50 ihickson 1414:
1.123 ihickson 1415: <!-- v2-onclose
1.81 ihickson 1416: <li>
1.50 ihickson 1417:
1.123 ihickson 1418: <p>For each <code>Worker</code> or <code>SharedWorker</code>
1.81 ihickson 1419: object associated with <var title="">worker global scope</var>,
1420: <span>queue a task</span> to <span>fire a simple event</span>
1.115 ihickson 1421: called <code title="event-close">close</code> at that object.</p>
1.5 ihickson 1422:
1.81 ihickson 1423: </li>
1.123 ihickson 1424: -->
1.155 ihickson 1425: </ol><hr><p>When a user agent is to <dfn id="kill-a-worker">kill a worker</dfn> it must
1.81 ihickson 1426: run the following steps in parallel with the worker's main loop (the
1.155 ihickson 1427: "<a href="#run-a-worker">run a worker</a>" processing model defined above):<ol><!-- v2-onclose
1.123 ihickson 1428: <li><p>If the worker's <code>WorkerGlobalScope</code> object's
1429: <span title="dom-WorkerGlobalScope-closing">closing</span> flag is
1.81 ihickson 1430: false, <span>queue a task</span> to <span>fire a simple
1.115 ihickson 1431: event</span> called <code title="event-close">close</code> at the
1.123 ihickson 1432: worker's <code>WorkerGlobalScope</code> object.</p></li>
1.155 ihickson 1433: --><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 1434: true.</li>
1435:
1.123 ihickson 1436: <!-- v2-onclose
1437: <li><p>Wait a user-agent-defined amount of time. If the "<span>run
1438: a worker</span>" processing model defined above immediately starts
1439: running event listeners registered for the <code
1440: title="event-close">close</code> event, this time should not be
1441: zero — the idea is that the <code
1442: title="event-close">close</code> event can be used to clean up
1443: when shutting down unexpectedly.</p></li>
1444: -->
1.81 ihickson 1445:
1.115 ihickson 1446: <li><p>If there are any <span title="concept-task">tasks</span>
1.81 ihickson 1447: queued in the <span>event loop</span>'s <span title="task
1.123 ihickson 1448: queue">task queues</span><!-- v2-onclose other than the <code
1449: title="event-close">close</code> event that this algorithm just
1450: added-->, discard them without processing them.</li>
1.81 ihickson 1451:
1.123 ihickson 1452: <!-- v2-onclose
1.115 ihickson 1453: <li><p>If the <code title="event-close">close</code> event that
1.81 ihickson 1454: this algorithm just queued hasn't yet been dispatched, then abort
1.123 ihickson 1455: the script currently running in the worker.</p></li>
1456: -->
1.81 ihickson 1457:
1458: <li><p>Wait a user-agent-defined amount of time.</li>
1459:
1.123 ihickson 1460: <li><p>Abort the script currently running in the worker<!--
1461: v2-onclose (if any script is running, then it will be a handler for
1462: the <code title="event-close">close</code> event)-->.</li>
1.81 ihickson 1463:
1.155 ihickson 1464: </ol><p>User agents may invoke the "<a href="#kill-a-worker">kill a worker</a>"
1.81 ihickson 1465: processing model on a worker at any time, e.g. in response to user
1466: requests, in response to CPU quota management, or when a worker
1.115 ihickson 1467: stops being an <a href="#active-needed-worker">active needed worker</a> if the worker
1468: continues executing even after its <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag was
1.155 ihickson 1469: 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 1470: the following steps in parallel with the worker's main loop (the
1.155 ihickson 1471: "<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 1472: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag to
1.81 ihickson 1473: true.</li>
1474:
1.115 ihickson 1475: <li><p>If there are any <span title="concept-task">tasks</span>
1.81 ihickson 1476: queued in the <span>event loop</span>'s <span title="task
1477: queue">task queues</span>, discard them without processing
1478: them.</li>
1479:
1480: <li><p>Abort the script currently running in the worker.</li>
1481:
1.115 ihickson 1482: <li><p>If the worker's <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object is
1483: actually a <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code> object (i.e. the
1.81 ihickson 1484: worker is a dedicated worker), then empty the <span>port message
1485: queue</span> of the port that the worker's implicit port is
1486: entangled with.</li>
1487:
1.155 ihickson 1488: </ol><hr><p>The <span>task source</span> for the tasks mentioned above is the
1489: <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 1490: worker's scripts, if the error did not occur while handling a
1491: previous script error, the user agent must <span>report the
1492: 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>
1.155 ihickson 1493: attribute. <a href="#refsHTML5">[HTML5]</a><p>For shared workers, if the error is still <i title="concept-error-nothandled">not handled</i> afterwards, or if
1.132 ihickson 1494: the error occurred while handling a previous script error, the error
1.155 ihickson 1495: should be reported to the user. <a href="#refsHTML5">[HTML5]</a><p>For dedicated workers, if the error is still <i title="concept-error-nothandled">not handled</i> afterwards, or if
1.132 ihickson 1496: the error occurred while handling a previous script error, the user
1.123 ihickson 1497: agent must <span>queue a task</span> to <a href="#fire-a-worker-error-event">fire a worker error
1498: event</a> at the <code><a href="#worker">Worker</a></code> object associated with the
1.155 ihickson 1499: worker.<p>When the user agent is to <dfn id="fire-a-worker-error-event">fire a worker error event</dfn> at
1.118 ihickson 1500: a <code><a href="#worker">Worker</a></code> object, it must dispatch an event that uses
1501: the <code><a href="#errorevent">ErrorEvent</a></code> interface, with the name <code title="event-error">error</code>, that doesn't bubble and is
1.115 ihickson 1502: 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 set
1.81 ihickson 1503: appropriately. The default action of this event depends on whether
1.115 ihickson 1504: the <code><a href="#worker">Worker</a></code> object is itself in a worker. If it is, and
1.81 ihickson 1505: that worker is also a dedicated worker, then the user agent must
1.118 ihickson 1506: again <span>queue a task</span> to <a href="#fire-a-worker-error-event">fire a worker error
1507: event</a> at the <code><a href="#worker">Worker</a></code> object associated with
1508: <em>that</em> worker. Otherwise, then the error should be reported
1.155 ihickson 1509: to the user.<p>The <span>task source</span> for the tasks mentioned above is the
1510: <span>DOM manipulation task source</span>.<hr><pre class="idl">interface <dfn id="errorevent">ErrorEvent</dfn> : Event {
1.147 ihickson 1511: readonly attribute DOMString <a href="#dom-errorevent-message" title="dom-ErrorEvent-message">message</a>;
1512: readonly attribute DOMString <a href="#dom-errorevent-filename" title="dom-ErrorEvent-filename">filename</a>;
1.115 ihickson 1513: readonly attribute unsigned long <a href="#dom-errorevent-lineno" title="dom-ErrorEvent-lineno">lineno</a>;
1.147 ihickson 1514: void <a href="#dom-errorevent-initerrorevent" title="dom-ErrorEvent-initErrorEvent">initErrorEvent</a>(in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in DOMString messageArg, in DOMString filenameArg, in unsigned long linenoArg);
1515: void <a href="#dom-errorevent-initerroreventns" title="dom-ErrorEvent-initErrorEventNS">initErrorEventNS</a>(in DOMString namespaceURIArg, in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in DOMString messageArg, in DOMString filenameArg, in unsigned long linenoArg);
1.155 ihickson 1516: };</pre><p>The <dfn id="dom-errorevent-initerrorevent" title="dom-ErrorEvent-initErrorEvent"><code>initErrorEvent()</code></dfn>
1.115 ihickson 1517: and <dfn id="dom-errorevent-initerroreventns" title="dom-ErrorEvent-initErrorEventNS"><code>initErrorEventNS()</code></dfn>
1.81 ihickson 1518: methods must initialize the event in a manner analogous to the
1.155 ihickson 1519: similarly-named methods in the DOM Events interfaces. <a href="#refsDOMEVENTS">[DOMEVENTS]</a><p>The <dfn id="dom-errorevent-message" title="dom-ErrorEvent-message"><code>message</code></dfn>
1520: attribute represents the error message.<p>The <dfn id="dom-errorevent-filename" title="dom-ErrorEvent-filename"><code>filename</code></dfn>
1.81 ihickson 1521: attribute represents the <span>absolute URL</span> of the script in
1.155 ihickson 1522: which the error originally occurred.<p>The <dfn id="dom-errorevent-lineno" title="dom-ErrorEvent-lineno"><code>lineno</code></dfn>
1.132 ihickson 1523: attribute represents the line number where the error occurred in the
1.155 ihickson 1524: 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">interface <dfn id="abstractworker">AbstractWorker</dfn> {
1.144 ihickson 1525: attribute <span>Function</span> <a href="#handler-abstractworker-onerror" title="handler-AbstractWorker-onerror">onerror</a>;
1526: <!-- v2-onclose attribute <span>Function</span> <span title="handler-AbstractWorker-onclose">onclose</span>; -->
1.172 ihickson 1527: };
1.177 ihickson 1528: <a href="#abstractworker">AbstractWorker</a> implements <span>EventTarget</span>;</pre><p>The following are the <span>event handlers</span> (and their
1529: corresponding <span title="event handler event type">event handler
1530: event types</span>) that must be supported, as IDL attributes, by
1531: 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 1532: <tbody><tr><td><dfn id="handler-abstractworker-onerror" title="handler-AbstractWorker-onerror"><code>onerror</code></dfn> <td> <code title="event-error">error</code>
1.123 ihickson 1533: <!-- v2-onclose <tr><td><dfn title="handler-AbstractWorker-onclose"><code>onclose</code></dfn> <td> <code title="event-close">close</code> -->
1.155 ihickson 1534: </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>(in DOMString scriptURL)]
1.115 ihickson 1535: interface <dfn id="worker">Worker</dfn> : <a href="#abstractworker">AbstractWorker</a> {
1536: void <a href="#dom-worker-terminate" title="dom-Worker-terminate">terminate</a>();
1.50 ihickson 1537:
1.174 ihickson 1538: void <a href="#dom-worker-postmessage" title="dom-Worker-postMessage">postMessage</a>(in any message, in optional <span>MessagePortArray</span> ports);<!--
1.81 ihickson 1539: <span>MessagePort</span> <span title="dom-Worker-startConversation">startConversation</span>(in any message);-->
1.144 ihickson 1540: attribute <span>Function</span> <a href="#handler-worker-onmessage" title="handler-Worker-onmessage">onmessage</a>;
1.155 ihickson 1541: };</pre><p>The <dfn id="dom-worker-terminate" title="dom-Worker-terminate"><code>terminate()</code></dfn> method,
1.115 ihickson 1542: when invoked, must cause the "<a href="#terminate-a-worker">terminate a worker</a>"
1.81 ihickson 1543: algorithm to be run on the worker with with the object is
1.155 ihickson 1544: associated.<p><code><a href="#worker">Worker</a></code> objects act as if they had an implicit
1.81 ihickson 1545: <code>MessagePort</code> associated with them. This port is part of
1546: a channel that is set up when the worker is created, but it is not
1547: exposed. This object must never be garbage collected before the
1.155 ihickson 1548: <code><a href="#worker">Worker</a></code> object.<p>All messages received by that port must immediately be retargeted
1549: 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><!--
1.64 ihickson 1550: and <dfn
1551: title="dom-Worker-startConversation"><code>startConversation()</code></dfn>-->
1.115 ihickson 1552: method<!--s (startConversation)--> on <code><a href="#worker">Worker</a></code> objects
1.81 ihickson 1553: must act as if, when invoked, it<!--/they (startConversation)-->
1554: immediately invoked the method of the same name on the port, with
1.177 ihickson 1555: the same arguments, and returned the same return value.<p>The following are the <span>event handlers</span> (and their
1556: corresponding <span title="event handler event type">event handler
1557: event types</span>) that must be supported, as IDL attributes, by
1558: 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 1559: <tbody><tr><td><dfn id="handler-worker-onmessage" title="handler-Worker-onmessage"><code>onmessage</code></dfn> <td> <code title="event-message">message</code>
1560: </table><hr><p>When the <dfn id="dom-worker" title="dom-Worker"><code>Worker(<var title="">scriptURL</var>)</code></dfn> constructor is invoked, the
1561: 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>first
1.133 ihickson 1562: script</span>'s <span title="script's base URL">base URL</span>,
1563: when the method is invoked.</li>
1.9 ihickson 1564:
1.81 ihickson 1565: <li><p>If this fails, throw a <code>SYNTAX_ERR</code>
1566: exception.</li>
1.9 ihickson 1567:
1.167 ihickson 1568: <li>
1569:
1570: <p>If the <span>origin</span> of the resulting <span>absolute
1571: URL</span> is not the <span title="same origin">same</span> as the
1.176 ihickson 1572: origin of the <span>first script</span>, then throw a
1573: <span>security exception</span>.</p>
1.167 ihickson 1574:
1575: <p class="note">Thus, scripts must be external files with the same
1576: scheme as the original page: you can't load a script from a <code title="">data:</code> URL or <code title="">javascript:</code>
1577: URL, and a <code>http:</code> page couldn't start workers using
1578: scripts with <code>http:</code> URLs.</p>
1579:
1580: </li>
1.9 ihickson 1581:
1.115 ihickson 1582: <li><p><span>Create a new <code><a href="#dedicatedworkerglobalscope">DedicatedWorkerGlobalScope</a></code>
1.81 ihickson 1583: object</span>. Let <var title="">worker global scope</var> be this
1584: new object.</li>
1.9 ihickson 1585:
1.115 ihickson 1586: <li><p>Create a new <code><a href="#worker">Worker</a></code> object, associated with
1.81 ihickson 1587: <var title="">worker global scope</var>. Let <var title="">worker</var> be this new object.</li>
1.50 ihickson 1588:
1.81 ihickson 1589: <li><p><span>Create a <code>MessagePort</code> object</span> owned
1.123 ihickson 1590: by the <span title="script's global scope">global scope</span> of
1591: the <span title="concept-script">script</span> that invoked the
1592: constructor. Let this be the <var title="">outside
1.81 ihickson 1593: port</var>.</li>
1.9 ihickson 1594:
1.81 ihickson 1595: <li><p>Associate the <var title="">outside port</var> with <var title="">worker</var>.</li>
1.50 ihickson 1596:
1.81 ihickson 1597: <li><p><span>Create a <code>MessagePort</code> object</span> owned
1598: by <var title="">worker global scope</var>. Let <var title="">inside port</var> be this new object.</li>
1.50 ihickson 1599:
1.81 ihickson 1600: <li><p>Associate <var title="">inside port</var> with <var title="">worker global scope</var>.</li>
1.50 ihickson 1601:
1.81 ihickson 1602: <li><p><span>Entangle</span> <var title="">outside port</var> and
1603: <var title="">inside port</var>.</li>
1.50 ihickson 1604:
1.81 ihickson 1605: <li><p>Return <var title="">worker</var>, and run the following
1606: steps asynchronously.</li>
1.50 ihickson 1607:
1.126 ihickson 1608: <li><p>Enable <var title="">inside port</var>'s <span>port message
1.81 ihickson 1609: queue</span>.</li>
1.50 ihickson 1610:
1.126 ihickson 1611: <li><p>Enable <var title="">outside port</var>'s <span>port message
1.81 ihickson 1612: queue</span>.</li>
1.50 ihickson 1613:
1614: <li>
1.51 ihickson 1615:
1.123 ihickson 1616: <p>Let <var title="">docs</var> be the <a href="#list-of-relevant-document-objects-to-add">list of relevant
1617: <code>Document</code> objects to add</a> given the <span title="script's global scope">global scope</span> of the <span title="concept-script">script</span> that invoked the
1618: constructor.</p>
1619:
1620: </li>
1621:
1622: <li>
1623:
1624: <p><a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">Add to
1625: <var title="">worker global scope</var>'s list of <span>the
1626: worker's <code>Document</code>s</span></a> the
1627: <code>Document</code> objects in <var title="">docs</var>.</p>
1628:
1629: </li>
1630:
1631: <li>
1632:
1.124 ihickson 1633: <p>If the <span title="script's global scope">global scope</span>
1634: of the <span title="concept-script">script</span> that invoked the
1635: constructor is a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object (i.e. we
1636: are creating a nested worker), add <var title="">worker global
1637: scope</var> to the list of <a href="#the-worker-s-workers">the worker's workers</a> of the
1638: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object that is the <span title="script's global scope">global scope</span> of the <span title="concept-script">script</span> that invoked the
1639: constructor.</p>
1640:
1641: </li>
1642:
1643: <li>
1644:
1.115 ihickson 1645: <p><a href="#run-a-worker">Run a worker</a> for the resulting <span>absolute
1.81 ihickson 1646: URL</span>, with the <span>script browsing context</span> of the
1647: script that invoked the method as the <var title="">owner browsing
1.176 ihickson 1648: context</var>, with the <span>origin</span> of the <span>first
1649: script</span> as the <var title="">owner origin</var>, and with
1650: <var title="">worker global scope</var> as the global scope.</p>
1.9 ihickson 1651:
1.81 ihickson 1652: </li>
1.4 ihickson 1653:
1.155 ihickson 1654: </ol><p>This constructor must be visible when the <span>script's global
1.135 ihickson 1655: scope</span> is either a <code>Window</code> object or an object
1.174 ihickson 1656: 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>(in DOMString scriptURL, in optional DOMString name)]
1.115 ihickson 1657: interface <dfn id="sharedworker">SharedWorker</dfn> : <a href="#abstractworker">AbstractWorker</a> {
1658: readonly attribute <span>MessagePort</span> <a href="#dom-sharedworker-port" title="dom-SharedWorker-port">port</a>;
1.155 ihickson 1659: };</pre><p>The <dfn id="dom-sharedworker-port" title="dom-SharedWorker-port"><code>port</code></dfn>
1.81 ihickson 1660: attribute must return the value it was assigned by the object's
1661: constructor. It represents the <code>MessagePort</code> for
1.155 ihickson 1662: 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 1663: constructor is invoked, the user agent must run the following
1.155 ihickson 1664: steps:<ol><li><p><span title="resolve a url">Resolve</span> the <var title="">scriptURL</var> argument.</li>
1.81 ihickson 1665:
1666: <li><p>If this fails, throw a <code>SYNTAX_ERR</code>
1667: exception.</li>
1668:
1.159 ihickson 1669: <li><p>Otherwise, let <var title="">scriptURL</var> be the
1670: resulting <span>absolute URL</span>.</li>
1671:
1672: <li><p>Let <var title="">name</var> be the value of the second
1.164 ihickson 1673: argument, or the empty string if the second argument was
1674: omitted.</li>
1.159 ihickson 1675:
1.167 ihickson 1676: <li>
1677:
1678: <p>If the <span>origin</span> of <var title="">scriptURL</var> is
1679: not the <span title="same origin">same</span> as the origin of the
1.176 ihickson 1680: <span>first script</span>, then throw a <span>security
1.167 ihickson 1681: exception</span>.</p>
1682:
1683: <p class="note">Thus, scripts must be external files with the same
1684: scheme as the original page: you can't load a script from a <code title="">data:</code> URL or <code title="">javascript:</code>
1685: URL, and a <code>http:</code> page couldn't start workers using
1686: scripts with <code>http:</code> URLs.</p>
1687:
1688: </li>
1.9 ihickson 1689:
1690: <li>
1691:
1.123 ihickson 1692: <p>Let <var title="">docs</var> be the <a href="#list-of-relevant-document-objects-to-add">list of relevant
1693: <code>Document</code> objects to add</a> given the <span title="script's global scope">global scope</span> of the <span title="concept-script">script</span> that invoked the
1694: constructor.</p>
1695:
1696: </li>
1697:
1698: <li>
1699:
1.50 ihickson 1700: <p>Execute the following substeps atomically:</p>
1.9 ihickson 1701:
1.155 ihickson 1702: <ol><li><p>Create a new <code><a href="#sharedworker">SharedWorker</a></code> object, which will
1.115 ihickson 1703: shortly be associated with a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1704: object. Let this <code><a href="#sharedworker">SharedWorker</a></code> object be <var title="">worker</var>.</li>
1.81 ihickson 1705:
1.123 ihickson 1706: <li><p><span>Create a <code>MessagePort</code> object</span>
1707: owned by the <span title="script's global scope">global
1708: scope</span> of the script that invoked the method. Let this be
1709: the <var title="">outside port</var>.</li>
1.81 ihickson 1710:
1.115 ihickson 1711: <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 1712:
1.164 ihickson 1713: <li><p>Let <var title="">worker global scope</var> be
1714: null.</li>
1715:
1716: <li><p>If <var title="">name</var> is not the empty string and
1717: there exists a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object whose
1718: <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a> flag
1719: is false, whose <code title="dom-WorkerGlobalScope-name">name</code> attribute is
1720: exactly equal to <var title="">name</var>, and whose <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1721: represents an <span>absolute URL</span> with the <span>same
1722: origin</span> as <var title="">scriptURL</var>, then let <var title="">worker global scope</var> be that
1723: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object.</li>
1724:
1725: <li><p>Otherwise, if <var title="">name</var> is the empty string
1726: and there exists a <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object
1727: whose <a href="#dom-workerglobalscope-closing" title="dom-WorkerGlobalScope-closing">closing</a>
1728: flag is false, and whose <code title="dom-WorkerGlobalScope-location"><a href="#dom-workerglobalscope-location">location</a></code> attribute
1729: is exactly equal to <var title="">scriptURL</var>, then let <var title="">worker global scope</var> be that
1730: <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code> object.</li>
1731:
1.9 ihickson 1732: <li>
1733:
1.164 ihickson 1734: <p>If <var title="">worker global scope</var> is not null, then
1735: run these steps:</p>
1.81 ihickson 1736:
1.164 ihickson 1737: <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 1738: attribute represents an <span>absolute URL</span> that is not
1.159 ihickson 1739: exactly equal to <var title="">scriptURL</var>, then throw a
1740: <code>URL_MISMATCH_ERR</code> exception and abort all these
1741: steps.</li>
1.81 ihickson 1742:
1743: <li><p>Associate <var title="">worker</var> with <var title="">worker global scope</var>.</li>
1744:
1745: <li><p><span>Create a <code>MessagePort</code> object</span>
1746: owned by <var title="">worker global scope</var>. Let this
1747: be the <var title="">inside port</var>.</li>
1748:
1749: <li><p><span>Entangle</span> <var title="">outside port</var>
1750: and <var title="">inside port</var>.</li>
1751:
1752: <li><p>Return <var title="">worker</var> and perform the next
1753: step asynchronously.</li>
1.9 ihickson 1754:
1.81 ihickson 1755: <li><p>Create an event that uses the <code>MessageEvent</code>
1.115 ihickson 1756: interface, with the name <code title="event-connect">connect</code>, which does not bubble, is
1.118 ihickson 1757: not cancelable, has no default action, has a <code title="dom-MessageEvent-data">data</code> attribute whose value
1758: is the empty string and has a <code title="dom-MessageEvent-ports">ports</code> attribute whose
1759: value is an array containing only the newly created port, and
1760: <span>queue a task</span> to dispatch the event at <var title="">worker global scope</var>.</li>
1.43 ihickson 1761:
1.123 ihickson 1762: <li>
1763:
1764: <p><a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">Add to
1765: <var title="">worker global scope</var>'s list of <span>the
1766: worker's <code>Document</code>s</span></a> the
1767: <code>Document</code> objects in <var title="">docs</var>.</p>
1768:
1769: </li>
1770:
1.124 ihickson 1771: <li>
1772:
1773: <p>If the <span title="script's global scope">global
1774: scope</span> of the <span title="concept-script">script</span>
1775: that invoked the constructor is a
1776: <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
1777: worker's workers</a> of the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1778: object that is the <span title="script's global scope">global
1779: scope</span> of the <span title="concept-script">script</span>
1780: that invoked the constructor.</p>
1781:
1782: </li>
1783:
1.81 ihickson 1784: <li><p>Abort all these steps.</li>
1.9 ihickson 1785:
1.155 ihickson 1786: </ol></li>
1.9 ihickson 1787:
1.115 ihickson 1788: <li><p><span>Create a new <code><a href="#sharedworkerglobalscope">SharedWorkerGlobalScope</a></code>
1.81 ihickson 1789: object</span>. Let <var title="">worker global scope</var> be
1790: this new object.</li>
1.9 ihickson 1791:
1.81 ihickson 1792: <li><p>Associate <var title="">worker</var> with <var title="">worker global scope</var>.</li>
1.9 ihickson 1793:
1.115 ihickson 1794: <li><p>Set the <code title="dom-SharedWorkerGlobalScope-name"><a href="#dom-sharedworkerglobalscope-name">name</a></code> attribute of
1.81 ihickson 1795: <var title="">worker global scope</var> to <var title="">name</var>.</li>
1.9 ihickson 1796:
1.81 ihickson 1797: <li><p><span>Create a <code>MessagePort</code> object</span>
1798: owned by <var title="">worker global scope</var>. Let <var title="">inside port</var> be this new object.</li>
1.9 ihickson 1799:
1.81 ihickson 1800: <li><p><span>Entangle</span> <var title="">outside port</var> and
1801: <var title="">inside port</var>.</li>
1.9 ihickson 1802:
1.155 ihickson 1803: </ol></li>
1.28 ihickson 1804:
1.123 ihickson 1805: <li><p>Return <var title="">worker</var> and perform the remaining
1806: steps asynchronously.</li>
1.18 ihickson 1807:
1.81 ihickson 1808: <li><p>Create an event that uses the <code>MessageEvent</code>
1.118 ihickson 1809: interface, with the name <code title="event-connect">connect</code>, which does not bubble, is not
1.115 ihickson 1810: cancelable, has no default action, has a <code title="dom-MessageEvent-data">data</code> attribute whose value is
1.118 ihickson 1811: the empty string and has a <code title="dom-MessageEvent-ports">ports</code> attribute whose value
1812: is an array containing only the newly created port, and <span>queue
1813: a task</span> to dispatch the event at <var title="">worker global
1814: scope</var>.</li>
1.26 ihickson 1815:
1816: <li>
1.46 ihickson 1817:
1.123 ihickson 1818: <p><a href="#add-a-document-to-the-worker-s-documents" title="add a document to the worker's documents">Add to
1819: <var title="">worker global scope</var>'s list of <span>the
1820: worker's <code>Document</code>s</span></a> the
1821: <code>Document</code> objects in <var title="">docs</var>.</p>
1822:
1823: </li>
1824:
1825: <li>
1826:
1.124 ihickson 1827: <p>If the <span title="script's global scope">global scope</span>
1828: of the <span title="concept-script">script</span> that invoked the
1829: 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
1830: worker's workers</a> of the <code><a href="#workerglobalscope">WorkerGlobalScope</a></code>
1831: object that is the <span title="script's global scope">global
1832: scope</span> of the <span title="concept-script">script</span>
1833: that invoked the constructor.</p>
1834:
1835: </li>
1836:
1837: <li>
1838:
1.159 ihickson 1839: <p><a href="#run-a-worker">Run a worker</a> for <var title="">scriptURL</var>,
1840: with the <span>script browsing context</span> of the script that
1841: invoked the method as the <var title="">owner browsing
1.176 ihickson 1842: context</var>, with the <span>origin</span> of the <span>first
1843: script</span> as the <var title="">owner origin</var>, and with
1844: <var title="">worker global scope</var> as the global scope.</p>
1.26 ihickson 1845:
1.60 ihickson 1846: </li>
1.81 ihickson 1847:
1.155 ihickson 1848: </ol><p>This constructor must be visible when the <span>script's global
1.135 ihickson 1849: scope</span> is either a <code>Window</code> object or an object
1.155 ihickson 1850: implementing the <code><a href="#workerutils">WorkerUtils</a></code> interface.<p>The <span>task source</span> for the tasks mentioned above is the
1851: <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">[Supplemental, NoInterfaceObject]
1.150 ihickson 1852: interface <dfn id="workerutils">WorkerUtils</dfn> {
1853: void <a href="#dom-workerglobalscope-importscripts" title="dom-WorkerGlobalScope-importScripts">importScripts</a>(in DOMString... urls);
1.115 ihickson 1854: readonly attribute <a href="#worker-navigator" title="worker-Navigator">Navigator</a> <a href="#dom-worker-navigator" title="dom-worker-navigator">navigator</a>;
1.150 ihickson 1855: };
1.172 ihickson 1856: <a href="#workerutils">WorkerUtils</a> implement <span>WindowTimers</span>;</pre><p>The DOM APIs (<code>Node</code> objects, <code>Document</code>
1.81 ihickson 1857: objects, etc) are not available to workers in this version of this
1.155 ihickson 1858: 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 1859: <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object, the user agent must run the
1.155 ihickson 1860: following steps:<ol><li><p>If there are no arguments, return without doing
1.81 ihickson 1861: anything. Abort these steps.</li>
1862:
1863: <li><p><span title="resolve a url">Resolve</span> each
1864: argument.</li>
1865:
1866: <li><p>If any fail, throw a <code>SYNTAX_ERR</code>
1867: exception.</li>
1868:
1869: <!--
1.67 ihickson 1870: <li><p>If any of the resulting <span title="absolute URL">absolute
1871: URLs</span> have an <span>origin</span> that is not the <span
1872: title="same origin">same</span> as the origin of the script that
1873: invoked the method, then throw a <span>security
1874: exception</span>.</p></li>
1875: -->
1.26 ihickson 1876:
1877: <li>
1.81 ihickson 1878:
1.45 ihickson 1879: <p>Attempt to <span>fetch</span> each resource identified by the
1.176 ihickson 1880: resulting <span title="absolute URLs">absolute URL</span>, from
1881: the <span>first script</span>'s <span>origin</span>.</p> <!-- not
1882: http-origin privacy sensitive -->
1.81 ihickson 1883:
1884: </li>
1.26 ihickson 1885:
1886: <li>
1887:
1.81 ihickson 1888: <p>For each argument in turn, in the order given, starting with
1889: the first one, run these substeps:</p>
1.26 ihickson 1890:
1.155 ihickson 1891: <ol><li>
1.26 ihickson 1892:
1.81 ihickson 1893: <p>Wait for the fetching attempt for the corresponding resource
1894: to complete.</p>
1.60 ihickson 1895:
1.81 ihickson 1896: <p>If the fetching attempt failed, throw a
1897: <code>NETWORK_ERR</code> exception and abort all these
1898: steps.</p>
1.45 ihickson 1899:
1.115 ihickson 1900: <p>If the attempt succeeds, then <a href="#decode-a-script-resource" title="decode a script
1.85 ihickson 1901: resource">decode the script resource</a> to obtain its <var title="">source</var>.</p>
1902:
1903: <p>Let <var title="">language</var> be JavaScript.</p>
1.61 ihickson 1904:
1.115 ihickson 1905: <p class="note">As with the worker's script, the script here is
1.81 ihickson 1906: always assumed to be JavaScript, regardless of the MIME
1.170 ihickson 1907: type.</p>
1.61 ihickson 1908:
1.81 ihickson 1909: </li>
1.26 ihickson 1910:
1.81 ihickson 1911: <li>
1.26 ihickson 1912:
1.81 ihickson 1913: <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
1914: same global object, browsing context, character encoding, base
1.115 ihickson 1915: URL, and script group as the <span title="concept-script">script</span> that was created by the
1916: worker's <a href="#run-a-worker">run a worker</a> algorithm.</p>
1.81 ihickson 1917:
1.115 ihickson 1918: <p>Let the newly created <span title="concept-script">script</span> run until it either
1.81 ihickson 1919: returns, fails to parse, fails to catch an exception, or gets
1.115 ihickson 1920: prematurely aborted by the "<a href="#kill-a-worker">kill a worker</a>" or
1921: "<a href="#terminate-a-worker">terminate a worker</a>" algorithms defined above.</p>
1.26 ihickson 1922:
1.170 ihickson 1923: <p>If it failed to parse, then throw a <code>SyntaxError</code>
1924: exception and abort all these steps.</p>
1.63 ihickson 1925:
1.81 ihickson 1926: <p>If an exception was raised or if the script was prematurely
1927: aborted, then abort all these steps, letting the exception or
1928: aborting continue to be processed by the script that called the
1.115 ihickson 1929: <code title="dom-WorkerGlobalScope-importScripts"><a href="#dom-workerglobalscope-importscripts">importScripts()</a></code>
1.81 ihickson 1930: method.</p>
1931:
1.115 ihickson 1932: <p>If the "<a href="#kill-a-worker">kill a worker</a>" or "<a href="#terminate-a-worker">terminate a
1.81 ihickson 1933: worker</a>" algorithms abort the script then abort all these
1934: steps.</p>
1935:
1936: </li>
1937:
1.155 ihickson 1938: </ol></li>
1.152 ihickson 1939:
1.155 ihickson 1940: </ol><h3 id="the-navigator-object"><span class="secno">5.2 </span>The <code title="worker-Navigator"><a href="#worker-navigator">Navigator</a></code> object</h3><p>The <dfn id="dom-worker-navigator" title="dom-worker-navigator"><code>navigator</code></dfn> attribute
1.115 ihickson 1941: of the <code><a href="#workerutils">WorkerUtils</a></code> interface must return an instance of
1942: the <code title="worker-Navigator"><a href="#worker-navigator">Navigator</a></code> interface, which
1.93 ihickson 1943: represents the identity and state of the user agent (the
1.155 ihickson 1944: client):<pre class="idl">interface <dfn id="worker-navigator" title="worker-Navigator">Navigator</dfn> {};
1.150 ihickson 1945: <a href="#worker-navigator" title="worker-Navigator">Navigator</a> implements <span>NavigatorID</span>;
1.155 ihickson 1946: <a href="#worker-navigator" title="worker-Navigator">Navigator</a> implements <span>NavigatorOnLine</span>;</pre><p>Objects implementing the <code title="worker-Navigator"><a href="#worker-navigator">Navigator</a></code> interface also implement
1.150 ihickson 1947: the <code>NavigatorID</code> and <code>NavigatorOnLine</code>
1.155 ihickson 1948: interfaces. <a href="#refsHTML5">[HTML5]</a><p class="note">The <code title="worker-Navigator"><a href="#worker-navigator">Navigator</a></code>
1.93 ihickson 1949: interface defined in this specification is different than the one
1.155 ihickson 1950: defined in the HTML specification.<h3 id="apis-defined-in-other-specifications"><span class="secno">5.3 </span>APIs defined in other specifications</h3><p>The <code title="dom-opendatabase">openDatabase()</code> and
1.115 ihickson 1951: <code title="dom-opendatabase-sync">openDatabaseSync()</code>
1.155 ihickson 1952: methods are defined in the Web Database specification. <a href="#refsWEBDATABASE">[WEBDATABASE]</a><h3 id="interface-objects-and-constructors"><span class="secno">5.4 </span>Interface objects and constructors</h3><p>There must be no interface objects and constructors available in
1.81 ihickson 1953: the global scope of scripts whose <span>script execution
1.115 ihickson 1954: context</span> is a <code><a href="#workerglobalscope">WorkerGlobalScope</a></code> object except for
1.155 ihickson 1955: the following:<ul><li><p><code>XMLHttpRequest</code> and all interface objects and
1.81 ihickson 1956: constructors defined by the XMLHttpRequest specifications, except
1957: that the <span>document response entity body</span> must always be
1.160 ihickson 1958: null. The <span><code>XMLHttpRequest</code> base URL</span> is the
1959: <span>script's base URL</span>; the
1960: <span><code>XMLHttpRequest</code> origin</span> is the script's
1961: <span>origin</span>. <a href="#refsXHR">[XHR]</a></li>
1.81 ihickson 1962:
1963: <li><p>The <code>WebSocket</code> interface object and
1.152 ihickson 1964: constructor. <a href="#refsWEBSOCKET">[WEBSOCKET]</a></li>
1.81 ihickson 1965:
1.119 ihickson 1966: <li><p>The <code>EventSource</code> interface object and
1.152 ihickson 1967: constructor. <a href="#refsEVENTSOURCE">[EVENTSOURCE]</a></li>
1.119 ihickson 1968:
1.81 ihickson 1969: <li><p>The <code>MessageChannel</code> interface object and
1.152 ihickson 1970: constructor. <a href="#refsHTML5">[HTML5]</a></li>
1.81 ihickson 1971:
1.115 ihickson 1972: <li><p>The <code title="dom-Worker"><a href="#dom-worker">Worker()</a></code> and <code title="dom-SharedWorker"><a href="#dom-sharedworker">SharedWorker(<var title="">url</var>)</a></code> constructors.</li>
1.81 ihickson 1973:
1.155 ihickson 1974: </ul><h3 id="worker-locations"><span class="secno">5.5 </span>Worker locations</h3><pre class="idl">interface <dfn id="workerlocation">WorkerLocation</dfn> {
1.115 ihickson 1975: readonly attribute DOMString <a href="#dom-workerlocation-href" title="dom-WorkerLocation-href">href</a>;
1976: readonly attribute DOMString <a href="#dom-workerlocation-protocol" title="dom-WorkerLocation-protocol">protocol</a>;
1977: readonly attribute DOMString <a href="#dom-workerlocation-host" title="dom-WorkerLocation-host">host</a>;
1978: readonly attribute DOMString <a href="#dom-workerlocation-hostname" title="dom-WorkerLocation-hostname">hostname</a>;
1979: readonly attribute DOMString <a href="#dom-workerlocation-port" title="dom-WorkerLocation-port">port</a>;
1980: readonly attribute DOMString <a href="#dom-workerlocation-pathname" title="dom-WorkerLocation-pathname">pathname</a>;
1981: readonly attribute DOMString <a href="#dom-workerlocation-search" title="dom-WorkerLocation-search">search</a>;
1982: readonly attribute DOMString <a href="#dom-workerlocation-hash" title="dom-WorkerLocation-hash">hash</a>;
1.155 ihickson 1983: };</pre><p>A <code><a href="#workerlocation">WorkerLocation</a></code> object represents an <span>absolute
1984: URL</span> set at its creation.<p>The <dfn id="dom-workerlocation-href" title="dom-WorkerLocation-href"><code>href</code></dfn>
1.81 ihickson 1985: attribute must return the <span>absolute URL</span> that the object
1.155 ihickson 1986: represents.<p>The <code><a href="#workerlocation">WorkerLocation</a></code> interface also has the complement
1.163 ihickson 1987: of <span>URL decomposition IDL attributes</span>, <dfn id="dom-workerlocation-protocol" title="dom-WorkerLocation-protocol"><code>protocol</code></dfn>,
1.115 ihickson 1988: <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>,
1989: <dfn id="dom-workerlocation-pathname" title="dom-WorkerLocation-pathname"><code>pathname</code></dfn>,
1990: <dfn id="dom-workerlocation-search" title="dom-WorkerLocation-search"><code>search</code></dfn>,
1991: and <dfn id="dom-workerlocation-hash" title="dom-WorkerLocation-hash"><code>hash</code></dfn>. These must
1.163 ihickson 1992: follow the rules given for URL decomposition IDL attributes, with the
1.115 ihickson 1993: <span title="concept-uda-input">input</span> being the
1.81 ihickson 1994: <span>absolute URL</span> that the object represents (same as the
1.115 ihickson 1995: <code title="dom-WorkerLocation-href"><a href="#dom-workerlocation-href">href</a></code> attribute), and
1996: the <span title="concept-uda-setter">common setter action</span>
1.178 ! ihickson 1997: being a no-op, since the attributes are defined to be readonly. <a href="#refsHTML5">[HTML5]</a></p><!--START vCard--><!--START vEvent--><h2 class="no-num" id="references">References</h2><!--REFS--><!--END vCard--><!--END vEvent--><p>All references are normative unless marked "Non-normative".</p><!--START vCard--><!--START vEvent--><dl><dt id="refsDOMCORE">[DOMCORE]</dt>
1.153 ihickson 1998: <dd><cite><a href="http://www.w3.org/TR/DOM-Level-3-Core/">Document
1999: Object Model (DOM) Level 3 Core Specification</a></cite>, A. Le
2000: Hors, P. Le Hegaret, L. Wood, G. Nicol, J. Robie, M. Champion,
2001: S. Byrnes. W3C, April 2004.</dd>
2002: <!--
2003: <dd><cite><a href="http://simon.html5.org/specs/web-dom-core">Web
2004: DOM Core</a></cite>, S. Pieters. W3C, June 2009.</dd>
2005: -->
2006:
1.152 ihickson 2007: <dt id="refsDOMEVENTS">[DOMEVENTS]</dt>
2008: <!--
2009: <dd><cite><a
2010: href="http://www.w3.org/TR/DOM-Level-3-Events/">Document Object
2011: Model (DOM) Level 3 Events Specification</a></cite>,
2012: B. Höhrmann, P. Le Hegaret, T. Pixley. W3C, December
2013: 2007.</dd>
2014: -->
2015: <dd><cite><a href="http://dev.w3.org/2006/webapi/DOM-Level-3-Events/html/DOM3-Events.html">Document
2016: Object Model (DOM) Level 3 Events Specification</a></cite>,
2017: D. Schepers. W3C, July 2009.</dd>
2018:
2019: <dt id="refsECMA262">[ECMA262]</dt>
2020: <dd><cite><a href="http://www.ecma-international.org/publications/standards/Ecma-262.htm">ECMAScript
2021: Language Specification</a></cite>. ECMA, December 1999.</dd>
2022:
2023: <dt id="refsEVENTSOURCE">[EVENTSOURCE]</dt>
2024: <!--
2025: <dd><cite><a href="http://www.w3.org/TR/eventsource/">Server-Sent
2026: Events</a></cite>, I. Hickson. W3C, April 2009.</dd>
2027: -->
2028: <dd><cite><a href="http://dev.w3.org/html5/eventsource/">Server-Sent
2029: Events</a></cite>, I. Hickson. W3C, July 2009.</dd>
2030:
2031: <dt id="refsHTML5">[HTML5]</dt>
2032: <!--
1.161 ihickson 2033: <dd><cite><a href="http://www.w3.org/TR/html5/">HTML5</a></cite>,
1.152 ihickson 2034: I. Hickson, D. Hyatt. W3C, April 2009.</dd>
1.161 ihickson 2035: <dd><cite><a
2036: href="http://www.w3.org/html/wg/html5/">HTML5</a></cite>,
2037: I. Hickson, D. Hyatt. W3C, August 2009.</dd>
1.152 ihickson 2038: -->
1.161 ihickson 2039: <dd><cite><a href="http://www.whatwg.org/specs/web-apps/current-work/">HTML5</a></cite>,
2040: I. Hickson. WHATWG, August 2009.</dd>
1.152 ihickson 2041:
1.154 ihickson 2042: <dt id="refsRFC2119">[RFC2119]</dt>
2043: <dd><cite><a href="http://www.ietf.org/rfc/rfc2119.txt">Key words for use in
2044: RFCs to Indicate Requirement Levels</a></cite>, S. Bradner. IETF, March
2045: 1997.</dd>
2046:
1.152 ihickson 2047: <dt id="refsWEBDATABASE">[WEBDATABASE]</dt>
2048: <dd><cite><a href="http://dev.w3.org/html5/webdatabase/">Web
2049: Database</a></cite>, I. Hickson. W3C, July
2050: 2009.</dd>
2051:
1.154 ihickson 2052: <dt id="refsWEBIDL">[WEBIDL]</dt>
2053: <!--
2054: <dd><cite><a href="http://www.w3.org/TR/WebIDL/">Web
2055: IDL</a></cite>, C. McCormack. W3C, December 2008.</dd>
2056: -->
2057: <dd><cite><a href="http://dev.w3.org/2006/webapi/WebIDL/">Web
2058: IDL</a></cite>, C. McCormack. W3C, July 2009.</dd>
2059:
1.152 ihickson 2060: <dt id="refsWEBSOCKET">[WEBSOCKET]</dt>
2061: <!--
2062: <dd><cite><a href="http://www.w3.org/TR/websockets/">The Web Sockets
2063: API</a></cite>, I. Hickson. W3C, April
2064: 2009.</dd>
2065: -->
2066: <dd><cite><a href="http://dev.w3.org/html5/websockets/">The Web Sockets
2067: API</a></cite>, I. Hickson. W3C, August
2068: 2009.</dd>
2069:
2070: <dt id="refsXHR">[XHR]</dt>
2071: <!--
2072: <dd><cite><a href="http://www.w3.org/TR/XMLHttpRequest/">The XMLHttpRequest
2073: Object</a></cite>, A. van Kesteren. W3C, April
2074: 2008.</dd>
2075: -->
1.160 ihickson 2076: <dd><cite><a href="http://dev.w3.org/2006/webapi/XMLHttpRequest-2/"><code>XMLHttpRequest</code></a></cite>,
1.152 ihickson 2077: A. van Kesteren. W3C, June 2009.</dd>
2078:
1.178 ! ihickson 2079: </dl><!--END vCard--><!--END vEvent--><h2 class="no-num" id="acknowledgements">Acknowledgements</h2><!-- ACKS --><p>Thanks to
1.81 ihickson 2080:
2081: Aaron Boodman,
1.155 ihickson 2082: Алексей Проскуряков (Alexey Proskuryakov),
1.81 ihickson 2083: Anne van Kesteren,
2084: Ben Turner,
2085: Dmitry Titov,
1.96 ihickson 2086: Drew Wilson,
1.97 ihickson 2087: Jeremy Orlow,
1.81 ihickson 2088: Jonas Sicking,
2089: Justin James,
2090: Kevin Hakanson,
2091: Maciej Stachowiak,
2092: Michael Nordman,
2093: Mike Smith,
2094:
2095: and
2096:
2097: Philip Taylor
2098:
1.155 ihickson 2099: for their useful and substantial comments.<p>Huge thanks to the whole Gears team, who pioneered this
1.81 ihickson 2100: technology and whose experience has been a huge influence on this
1.155 ihickson 2101: specification.
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