Mozilla今日发布Mozilla Firefox 40.0的Beta 1版本，基于Gecko 40内核开发，40版本的最大改进是有望带来类似Chrome的多进程设计，这样可以提升内存的利用率从而提升性能和标签/窗口之间的稳定性(但最新的版本似乎并没有带来)，新设计的标签页可以自动判断和展示您认为感兴趣的内容，正式版本预计8月11日发布。

下载地址:

http://dm-download02.mozilla.org/pub/mozilla.org/mozilla.org/firefox/releases/40.0b1/

Changes for Web developersDeveloper Tools

Highlights:

• Improvements to the Animations view

• Get help from MDN for CSS property syntax

• Edit filters in the Page Inspector

• Web Console now shows messages from workers

• Filter requests by URL in the Network Monitor

• Many new context menu options in the Network Monitor

• Show when network resources are fetched from the browser cache

• Filter rules in the Page Inspector

More:

• Break at debugger; statements in unnamed eval sources

• Copy URL/Open in New Tab context menu items for Debugger source list pane

• console.dirxml support in the Web Console

• Style Editor: "Open Link In New Tab" item added to stylesheet list

• Inspector selector search now includes class/id results even without css prefix

• Tooltips in box-model view saying which CSS rule caused the value

• Switch between color unit format in the Inspector using Shift+click

• Implement "Scroll Into View" menu item for the Inspector

• Linkify url/id/resource attributes in the Inspector

• IP address tooltip in the Network Monitor

Everything: all devtools bugs fixed between Firefox 39 and Firefox 40.

CSS

• Prefixed rules (-moz-) for text-decoration-color, text-decoration-line, and text-decoration-style have been removed (bug 1097922).

• The property text-align now supports the match-parent value (bug 645642).

• In Quirks Mode, empty-cells now defaults to show, like in standard mode (bug 1020400).

• The -moz-orient non-standard property, used to style <meter> and <progress> element has been adapted for vertical writing-modes: the value auto has been dropped and the values inline and  block added, with inline being the new default value (bug 1028716).

HTML

No change.

JavaScript

• Unreachable code after return statement (including unreachable expression after semicolon-less return statements) will now show a warning in the console (bug 1005110, bug 1151931).

• Symbol.match has been added (bug 1054755).

• Passing an object which has a property named Symbol.match with a truthy value to String.prototype.startsWith, String.prototype.endsWith, and String.prototype.contains now throws a TypeError (bug 1054755).

• RegExp function returns pattern itself if called without new and pattern object has a property named Symbol.match with a truthy value, and the pattern object's constructor property equals to  RegExp function. (bug 1147817).

• Support for the non-standard JS1.7 destructuring for-in has been dropped (bug 1083498).

• Non-standard initializer expressions in for...in loops are now ignored and will present a warning in the console. (bug 748550 and bug 1164741).

• u{xxxxxx} Unicode code point escapes have been added (bug 320500).

• String.prototype.contains has been replaced with String.prototype.includes, String.prototype.contains is kept as an alias (bug 1102219).

• If the DataView constructor is called as a function without the new operator, a TypeError is now thrown as per the ES6 specification.

• An issue regressed in Firefox 21, where proxyfied arrays without the get trap were not working properly, has been fixed. If the get trap in a Proxy was not defined, Array.length returned 0 and the set trap didn't get called. A workaround was to add the get trap even if was not necessary in your code. This issue has been fixed now (bug 895223).

• WeakMap.prototype and WeakSet.prototype have been updated to be just ordinary objects, per ES6 specification (bug 1055473).

Interfaces/APIs/DOMNew APIs

• The Push API has been implemented (bug 1038811).

Web Animations API

Improvement in our experimental Web Animations implementation, mostley to match latest spec changes:

• AnimationPlayer.currentTime now can also be set (bug 1072037).

• Animatable.getAnimationPlayers(), available on Element has been renamed to Element.getAnimations() (bug 1145246).

• Animation and AnimationEffect have been merged into the newly created KeyframeEffectReadOnly (bug 1153734).

• AnimationPlayer has been renamed to Animation (bug 1154615).

• AnimationTimeline is now an abstract class, with DocumentTimeline its only implementation (bug 1152171).

CSSOM

• The CSS Font Loading API is now enabled by default in Nightly and Developer Edition releases (bug 1088437). It is still deactivated by default in Beta and Release browsers.

• The CSSCharsetRule interface has been removed and such objects are no longer available in CSSOM (bug 1148694). This matches the spec (recently adapted) and Chrome behavior.

WebRTC

• WebRTC: the negotiationneeded event is now also sent for initial negotiations, not only for re-negotiations (bug 1149838).

DOM & HTML DOM

• When unable to parse the srcset,  the HTMLImageElement.currentSrc method doesn't return null anymore but "", as requested by the latest specification (bug 1139560).

• Like for images, Firefox now throttle Window.requestAnimationFrame() for non-visible <iframe> (bug 1145439).

• Navigator.taintEnabled is no longer available for Web workers (bug 1154878).

• The read-only properties MouseEvent.offsetX and MouseEvent.offsetY have been implemented bug 69787.

Web Audio API

New extensions to the Web Audio API:

• The AudioContext.state and AudioContext.onstatechange properties as well as the methods AudioContext.suspend(), AudioContext.resume(), and AudioContext.close() have been added (bug 1094764).

• AudioBufferSourceNode now implements the AudioBufferSourceNode.detunek-rate attribute (bug 1153783).

Web Workers

• Slight improvement in our Service Worker API: the update() method has been moved from ServiceWorkerGlobalScope to ServiceWorkerRegistration (bug 1131350).

• ServiceWorkerRegistration is now available in Web workers (bug 1131327).

• DataStore is now available in Web workers (bug 949325).

IndexedDB

• IDBTransaction are now non-durable by default (bug 1112702). This favors performance over reliability and matches what other browsers are doing. For more information, read our durability definition.

Dev Tools

• The property Console.timeStamp has been added (bug 922221).

MathML

No change.

SVG

No change.

Audio/Video

No change.

Networking

No change.

Security

No change.

Changes for add-on and Mozilla developersXUL

No change.

JavaScript code modules

• Dict.jsm has been removed bug 1123309. Use Map instead.

XPCOM

No change.