path: root/files/zh-cn/mozilla/firefox/releases/44/index.html

---
title: Firefox 44 for developers
slug: Mozilla/Firefox/Releases/44
translation_of: Mozilla/Firefox/Releases/44
---
<div>{{FirefoxSidebar}}</div><p><a style="float: right; margin-bottom: 20px; padding: 10px; text-align: center; border-radius: 4px; display: inline-block; background-color: #81BC2E; white-space: nowrap; color: white; text-shadow: 0px 1px 0px rgba(0, 0, 0, 0.25); box-shadow: 0px 1px 0px 0px rgba(0, 0, 0, 0.2), 0px -1px 0px 0px rgba(0, 0, 0, 0.3) inset;" href="https://www.mozilla.org/firefox/developer/">为了测试火狐最新的开发人员特性，请安装火狐开发人员版（Firefox Developer Edition ）</a>Firefox 44 于2016年1月26号发布。这个页面列出了对开发人员有用的关键变化。</p>

<h2 id="对于Web开发人员的变化">对于Web开发人员的变化</h2>

<h3 id="开发者工具">开发者工具</h3>

<p>{{page('/en-US/docs/Tools/Release_notes', 'Firefox_44')}}</p>

<h3 id="HTML">HTML</h3>

<ul>
 <li><code><a href="/en-US/docs/Web/HTTP/Link_prefetching_FAQ">&lt;link rel="prefetch"&gt;</a></code> 现在服从 {{htmlattrxref("crossorigin", "link")}} 属性 ({{bug(1214819)}}).</li>
</ul>

<h3 id="CSS">CSS</h3>

<ul>
 <li><code>position:</code> <code>fixed;</code> 现在会创建一个新的层叠上下文 ({{bug(1179288)}}).</li>
 <li>默认支持 {{cssxref('unicode-range')}} ({{bug(1119062)}}).</li>
 <li>Our experimental implementation of CSS Writing Modes has been updated to reflect the latest specification:
  <ul>
   <li>The value <code>sideways</code> of the {{cssxref("text-orientation")}} property has been implemented and <code>sideways-right</code> has been made an alias of it ({{bug(1193488)}}).</li>
   <li>The value <code>sideways-rl</code> and <code>sideways-lr</code> of the {{cssxref("writing-mode")}} property ({{bug(1193488)}} and {{bug(1193519)}}).</li>
  </ul>
 </li>
 <li>The non-standard properties {{cssxref("-moz-math-display")}} and {{cssxref("-moz-window-shadow")}} are no more available from Web content ({{bug(1207002)}}, {{bug(1211040)}}, and {{bug(1212607)}}).</li>
 <li>The {{cssxref("font-style")}} property now distinguishes between <code>oblique</code> and <code>italic</code> when both variants are available ({{bug(543715)}}).</li>
 <li>Though not supported, the properties {{cssxref("marks")}}, {{cssxref("orphans")}}, {{cssxref("page")}}, {{cssxref("size")}}, and {{cssxref("widows")}}, were parsed and {{cssxref("@supports")}} was incorrectly reporting them as supported; this has been fixed and the properties are not parsed anymore, nor marked as supported ({{bug(1215702)}}).</li>
 <li>The internal value <code>-moz-mac-unified-toolbar</code> has been removed from the possible values for the {{cssxref("-moz-appearance")}} property ({{bug(1206468)}}).</li>
</ul>

<h3 id="JavaScript">JavaScript</h3>

<h4 id="New_APIs">New APIs</h4>

<ul>
 <li>{{jsxref("Symbol.toPrimitive")}}, {{jsxref("Symbol.prototype.@@toPrimitive", "Symbol.prototype[@@toPrimitive]")}}, and {{jsxref("Date.prototype.@@toPrimitive", "Date.prototype[@@toPrimitive]")}} have been implemented ({{bug(1054756)}}).</li>
</ul>

<h4 id="Changes">Changes</h4>

<ul>
 <li>The <code><a href="/en-US/docs/Web/JavaScript/Reference/Statements/let">let</a></code> and <code><a href="/en-US/docs/Web/JavaScript/Reference/Statements/const">const</a></code> bindings in the global level have been made compliant with ES2015 semantics. See {{bug(589199)}} and the blog post <a href="https://blog.mozilla.org/addons/2015/10/14/breaking-changes-let-const-firefox-nightly-44/">"Breaking changes in let and const in Firefox Nightly 44"</a>. In addition, <code>let</code> is now available to default Web JavaScript (strict and non-strict) and does not require a version opt-in anymore ({{bug(932517)}}).</li>
 <li>If <a href="/en-US/docs/Web/JavaScript/Typed_arrays">typed arrays'</a> (like {{jsxref("Int8Array", "Int8Array")}}) and {{jsxref("ArrayBuffer", "ArrayBuffer")}}) constructors are called as a function without the {{jsxref("Operators/new", "new")}} operator, a {{jsxref("TypeError")}} is now thrown as per the ES6 specification ({{bug(980945)}}, {{bug(1214936)}}).</li>
 <li>The {{jsxref("RegExp")}} sticky flag now follows the ES2015 standard for<a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/sticky#Anchored_sticky_flag"> anchored sticky regular expressions</a> ({{bug(773687)}}).</li>
 <li>The <a href="/en-US/docs/Mozilla/Projects/SpiderMonkey/Introduction_to_the_JavaScript_shell">JavaScript shell</a> (SpiderMonkey's REPL) now defaults to the default, Web-compatible JS version (and not JS1.7+ anymore) ({{bug(1192329)}}).</li>
</ul>

<h4 id="Removals">Removals</h4>

<ul>
 <li>Support for the non-standard <a href="/en-US/docs/Web/JavaScript/Reference/Statements/let#let_blocks"><code>let</code> blocks</a> has been dropped ({{bug(1167029)}}.</li>
 <li>The non-standard and deprecated property {{jsxref("Object.noSuchMethod", "Object.prototype.__noSuchMethod__")}} has been removed ({{bug(683218)}}).</li>
</ul>

<h3 id="InterfacesAPIsDOM">Interfaces/APIs/DOM</h3>

<h4 id="DOM_HTML_DOM">DOM &amp; HTML DOM</h4>

<ul>
 <li>For compatibility with specific existing sites, the property {{domxref("Document.charset")}} has been implemented as an alias of {{domxref("Document.characterSet")}} ({{bug(647621)}}).</li>
 <li>Support for the <code><a href="https://developer.mozilla.org/en-US/docs/Adding_search_engines_from_web_pages#Installing_Sherlock_plugins">window.sidebar.addSearchEngine()</a></code> method, which allowed Web pages to invoke an installation of a Sherlock plugin, has been dropped and now it just logs a warning in the Web Console ({{bug(862148)}}).</li>
 <li>To fight unwanted pop-ups, prompts requested in {{domxref("Window.onbeforeunload")}} of pages that have not been interacted with are no more displayed ({{bug(636905)}}).</li>
 <li>The deprecated method {{domxref("MessageEvent.initMessageEvent()")}} has been reimplemented for backward compatibility ({{bug(949376)}}).</li>
 <li>The obsolete property <code>DocumentType.internalSubset</code> has been removed ({{bug(801545)}}).</li>
 <li>For compatibility with existing sites, the properties {{domxref("Window.orientation")}} and {{domxref("Window.onorientationchange")}}, as well as the {{event("orientationchange")}} event have been implemented ({{bug(920734)}}).</li>
 <li>An {{HTMLElement("iframe")}} with explicit fullscreen request should not exit fullscreen implicitly ({{bug(1187801)}}).</li>
 <li>The events {{event("mouseover")}}, {{event("mouseout")}}, {{event("mouseenter")}}, {{event("mouseleave")}}, {{event("pointermove")}}, {{event("pointerover")}}, {{event("pointerout")}}, {{event("pointerenter")}} and {{event("pointerleave")}} are now triggered for disabled form elements ({{bug(218093)}}).</li>
 <li>The method {{domxref("Element.webkitMatchesSelector()")}} has been added ({{bug(1216193)}}) to improve interoperability.</li>
 <li>To match the spec, the method {{domxref("Document.createAttribute()")}} now converts the input to lower case ({{bug(1176313)}}).</li>
 <li>The non-standard <code>dialog</code> feature for {{domxref("Window.open()")}} is no longer available to Web content. It is still available to extensions and other code with chrome privileges ({{bug(1095236)}}.</li>
</ul>

<h4 id="Canvas">Canvas</h4>

<ul>
 <li>A new experimental {{domxref("OffscreenCanvas")}} API that allows rendering contexts (such as <a href="/en-US/docs/Web/API/WebGL_API">WebGL</a>) to run in <a href="/en-US/docs/Web/API/Web_Workers_API">Web Workers</a> has been implemented. To use this experimental API set <code>gfx.offscreencanvas.enabled</code> to <code>true</code> in about:config ({{bug(709490)}}). This API includes:

  <ul>
   <li>The {{domxref("OffscreenCanvas")}} interface,</li>
   <li>{{domxref("HTMLCanvasElement.transferControlToOffscreen()")}}, and</li>
   <li>{{domxref("WebGLRenderingContext.commit()")}}.</li>
   <li>Several WebGL interfaces are now also available in a worker context when this API is enabled.</li>
  </ul>
 </li>
</ul>

<h4 id="WebGL">WebGL</h4>

<ul>
 <li>Uniform Buffer Objects have been implemented ({{bug(1048747)}}).</li>
</ul>

<h4 id="IndexedDB">IndexedDB</h4>

<ul>
 <li>The {{domxref("IDBIndex.getAll()")}} and {{domxref("IDBIndex.getAllKeys()")}} are now available by default ({{bug(1196841)}}).</li>
</ul>

<h4 id="Service_Workers">Service Workers</h4>

<ul>
 <li>The {{domxref("ServiceWorkerMessageEvent")}} and {{domxref("ExtendableMessageEvent")}} interfaces have been implemented ({{bug(1143717)}} and {{bug(1207068)}}).</li>
 <li>{{domxref("Headers")}} objects now support a pair iterator, meaning that the methods {{domxref("Headers.entries()")}}, {{domxref("Headers.keys()")}}, and {{domxref("Headers.values()")}} are now available; {{jsxref("Symbol.iterator")}} now also returns the default iterator for them ({{bug(1108181)}}).</li>
 <li>The {{domxref('XMLHttpRequest')}} API has been disabled on Service Workers ({{bug(931243)}}).</li>
 <li>The interface {{domxref("FetchEvent")}} now extends {{domxref("ExtendableEvent")}}, giving it access to the {{domxref("ExtendableEvent.waitUntil()")}} method. ({{bug(1214772)}}).</li>
 <li>Following a recent change in the specification, {{domxref("FetchEvent.client")}} has been removed ({{bug(1218135)}}).</li>
 <li>To match the latest specification, the {{domxref("ServiceWorkerContainer.onreloadpage")}} has been removed ({{bug(1218139)}}).</li>
 <li>The event handlers {{domxref("ServiceWorkerGlobalScope.onbeforeevicted")}} and {{domxref("ServiceWorkerGlobalScope.onevicted")}} have been removed as they weren't following the spec. They will be reintroduced in the future, but their removal will allow feature detection to work as expected ({{bug(1218142)}}).</li>
 <li>In the {{domxref("FetchEvent.FetchEvent", "FetchEvent()")}} constructor, if the <code>isReload</code> member is not present in the options dictionary, it now defaults to <code>false</code> ({{bug(1216401)}}).</li>
 <li>The {{domxref("Client.frameType")}} property is now implemented on the right interface; it was on {{domxref("WindowClient")}} before ({{bug(1218146)}}).</li>
 <li>When <a href="/en-US/docs/Web/HTML/Using_the_application_cache">AppCache</a> is used to provide offline support for a page, a warning message is now displayed in the console advising developers to use <a href="/en-US/docs/Web/API/Service_Worker_API/Using_Service_Workers">Service workers</a> instead ({{bug("1204581")}}.)</li>
 <li>Service workers have been enabled by default in Gecko.</li>
</ul>

<h4 id="WebRTC">WebRTC</h4>

<ul>
 <li>WebRTC interfaces have been <em>unprefixed</em> ({{bug(1155923)}}). In particular:

  <ul>
   <li><code>mozRTCPeerConnection</code> is now {{domxref("RTCPeerConnection")}}.</li>
   <li><code>mozRTCIceCandidate</code> is now {{domxref("RTCIceCandidate")}}.</li>
   <li><code>mozRTCSessionDescription</code> is now {{domxref("RTCSessionDescription")}}.</li>
  </ul>
 </li>
 <li>The {{domxref("RTCDataChannel.bufferedAmountLowThreshold")}} and {{domxref("RTCDataChannel.onbufferedamountlow")}} properties, as well as the {{event("bufferedamountlow")}} event, have been implemented ({{bug(1178091)}}).</li>
 <li>The attribute {{domxref("RTCPeerConnection.canTrickleIceCandidates")}} has been added, the non-standard method {{domxref("RTCPeerConnection.updateIce()")}} removed ({{bug(1209744)}}).</li>
 <li>The {{domxref("MediaStream")}} interface now supports the {{domxref("MediaStream.addTrack()")}} and {{domxref("MediaStream.removeTrack()")}} methods ({{bug(1103188)}}).</li>
 <li>The constructor {{domxref("MediaStream.MediaStream", "MediaStream()")}} has been implemented ({{bug(1070216)}}).</li>
 <li>Support for the non-standard constraint style option list for {{domxref("RTCOfferOptions")}} has been removed; see <a href="https://www.fxsitecompat.com/en-USdocs/2015/constraint-like-rtcofferoptions-are-no-longer-supported/">this post on the site compatibility blog</a> for details.</li>
</ul>

<h4 id="New_APIs_2">New APIs</h4>

<ul>
 <li>An experimental implementation of the Canvas API in Workers has landed: {{domxref("OfflineCanvas")}} and {{domxref("HTMLCanvasElement.transferControlToOffscreen()")}} are available behind the <code>gfx.offscreencanvas.enabled</code> preference, currently disabled by default ({{bug(709490)}}).</li>
 <li>The Text2Speech API, part of Web Speech API, has now an OS X backend. But this is disabled by default ({{bug(1003452)}}).</li>
</ul>

<h4 id="Miscellaneous">Miscellaneous</h4>

<ul>
 <li>{{domxref("URLSearchParams")}} objects now support a pair iterator, meaning that the methods {{domxref("URLSearchParams.entries()")}}, {{domxref("URLSearchParams.keys()")}}, and {{domxref("URLSearchParams.values()")}} are now available; {{jsxref("Symbol.iterator")}} now also returns the default iterator for them ({{bug(1085284)}}).</li>
 <li>{{domxref("FormData")}} objects now support a pair iterator, meaning that the methods {{domxref("FormData.entries()")}}, {{domxref("FormData.keys")}}, and {{domxref("FormData.values()")}} are now available; {{jsxref("Symbol.iterator")}} now also returns the default iterator for them ({{bug(1127703)}}).</li>
 <li>When {{domxref("XMLHttpRequest.send()")}} is used with an HTML document, it now uses <code>text/html</code> instead of <code>application/xml</code> ({{bug(918771)}}).</li>
 <li>Speech synthesis (text-to-speech) has been implemented in Firefox Desktop for Mac and Linux, hidden behind the <code>media.webspeech.synth.enabled</code> flag in <code>about:config</code> ({{bug("1003452")}}, {{bug("1003464")}}.) See <a href="/en-US/docs/Web/API/Web_Speech_API">Web Speech API</a> for more information.</li>
 <li>Elements inside a {{HTMLElement("frame")}} or an {{HTMLElement('object')}} can't be set full-screen anymore ({{bug(1212299)}}).</li>
</ul>

<h3 id="MathML">MathML</h3>

<p><em>No change.</em></p>

<h3 id="SVG">SVG</h3>

<p><em>No change.</em></p>

<h3 id="AudioVideo">Audio/Video</h3>

<p><em>No change.</em></p>

<h2 id="HTTP">HTTP</h2>

<ul>
 <li>Support for the <a href="https://en.wikipedia.org/wiki/Brotli">Brotli</a> algorithm has been added and both <code><a href="/en-US/docs/Web/HTTP/Content_negotiation#The_Accept-Encoding_header">Accept-Encoding</a></code> and <code><a href="/en-US/docs/Web/HTTP/Headers/Content-Encoding">Content-Encoding </a></code>headers now support the <code>br</code> value ({{bug(366559)}} and {{bug(1211916)}}).</li>
 <li>Incorrect support of HTTP/2 headers containing line breaks (<code>'/n'</code>) have been removed as the spec doesn't allow it, unlike HTTP/1 ({{bug(1197847)}}).</li>
</ul>

<h2 id="Networking">Networking</h2>

<p><em>No change.</em></p>

<h2 id="Security">Security</h2>

<ul>
 <li>RC4 is now also disabled by default on Beta and Release versions of the browser ({{bug(1201025)}}) and the whitelist is now empty by default ({{bug(1215796)}}).</li>
</ul>

<h2 id="Changes_for_add-on_and_Mozilla_developers">Changes for add-on and Mozilla developers</h2>

<h3 id="Interfaces">Interfaces</h3>

<p><em>No change</em></p>

<h3 id="XUL">XUL</h3>

<p><em>No change.</em></p>

<h3 id="JavaScript_code_modules">JavaScript code modules</h3>

<ul>
 <li>Added <code>LIKE</code> support to {JSM("Sqlite.jsm")}} ({{bug(1188760)}}).</li>
 <li>Added <a href="/en-US/docs/Mozilla/Add-ons/Firefox_for_Android/API/Snackbars.jsm">Snackbars.jsm</a> module to <a href="/en-US/docs/Mozilla/Firefox_for_Android" title="/en/docs/Mozilla/Firefox_for_Android">Firefox for Android</a> ({{bug(1215026)}})</li>
</ul>

<h3 id="XPCOM">XPCOM</h3>

<ul>
 <li>The {{interface("nsIDOMWindow")}} interface is now empty. Its contents were either no longer used, had moved elsewhere, or were only used from C++. The items available from C++ code now reside in the <code>{{source("dom/base/nsPIDOMWindow.h", "nsPIDOMWindow")}}</code> interface ({{bug(1216401)}}).</li>
</ul>

<h3 id="Other">Other</h3>

<ul>
 <li>Due to breaking changes in Firefox 44 (<a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1202902">bug 1202902</a>), add-ons packed with <a href="/en-US/docs/Mozilla/Add-ons/SDK/Tools/cfx">cfx</a> will not work any longer. To make your add-on compatible again, please use <a href="/en-US/docs/Mozilla/Add-ons/SDK/Tools/jpm">jpm</a>. You can find steps to migrate from <em>cfx</em> to <em>jpm</em> <a href="/en-US/docs/Mozilla/Add-ons/SDK/Tools/cfx_to_jpm">here</a>.</li>
</ul>

<h2 id="See_also">See also</h2>

<ul>
 <li><a href="https://www.fxsitecompat.com/en-US/versions/44/">Site compatibility for Firefox 44</a></li>
</ul>

<h2 id="Older_versions">Older versions</h2>

<p>{{Firefox_for_developers(43)}}</p>