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Firefox 34 for developers 编辑

Firefox 34 was released on December 1st, 2014. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.

Changes for Web developers

Developer Tools

Highlights:

All devtools bugs fixed between Firefox 33 and Firefox 34.

CSS

Our experimental implementation of CSS Fonts Level 3 progresses. Newly implemented features are:
- the fallback algorithm of font-variant-position, creating synthetic alternates for missing glyphs, based on the subscript and superscript metrics supplied by the font (bug 1024804).
- The layout.css.font-features.enabled preference has been removed, meaning the following properties have been activated by default:
  - The CSS Font Level 3 version of font-variant which is now a shorthand property.
  - The longhand properties font-variant-caps, font-variant-numeric, font-variant-position, font-variant-east-asian, font-variant-ligatures, and font-variant-alternates.
  - The properties font-kerning and font-synthesis
  - The properties font-feature-settings and font-language-override are unprefixed. The prefixed version are still available for some time to ease transition.
The value auto has been added to min-width and min-height with a different behavior than the last time (bug 984711 and bug 1015474).
An experimental implementation, disabled by default, of the filter functional values of the filter property have been implemented. It is controlled by the layout.css.filters.enabled pref (bug 948265).
Fixed starting of CSS transitions that start together with changes to display, position, overflow, and similar properties (bug 625289)

HTML

No change.

JavaScript

The ES2015 syntax for computed property names on object literals has been implemented (bug 924688).
- This includes getter and setter method names as well (bug 1048384) and can also be used with destructuring.
The ES2015 shorthand syntax for defining methods on objects has been implemented (bug 924672).
The ES2015 Object method Object.assign() has been implemented (bug 937855).
ES2015 template strings and the String.raw() method are now supported (bug 1038259, bug 1039774).
A new ES2015 object WeakSet has been added (bug 792439).
ES2015 Symbols (only available in the Nightly channel) have been updated to conform with recent specification changes (bug 1042602):
- When trying to convert a symbol to a number, a TypeError will be thrown now.
- When using loose equality, Object(sym) == sym returns true now.
The experimental TypedArray.prototype.move() method (only available in former Nightly and Aurora channels) has been replaced with the now implemented standard ES2015 TypedArray.prototype.copyWithin() method (bug 1021379).
In strict mode, setting a duplicate property name in object literals will no longer throw a SyntaxError as per ES2015 specification (bug 1041128).
In regular expressions (including String.replace), the matched text for a capturing group is now undefined instead of the empty string when that capturing group didn't get consulted because quantifiers prevented its exercise (see bug 369778 and this example code). Note that due to web compatibility, RegExp.$N will still return an empty string (bug 1053944).
The ES2015 spread operator is now supported in destructuring (bug 933276).
Destructuring now uses iterator protocol instead of array-like protocol (bug 933276).
Proxy.revocable() has been implemented (bug 978279).

Interfaces/APIs/DOM

The Element.matches() method has been added; it does what the non-standard mozMatchesSelector() was doing (bug 886308).
The Performance.now() method is now available to Web workers (bug 908390).
The non-standard interface MozNamedAttrMap has been renamed to the standard NamedNodeMap and Element.attributes has been adapted to use it (bug 1055467).
The Path2D.addPath() method has been added (bug 985801).
The non-standard Device Storage API is now also enabled for privileged apps installed on Android (bug 886627).
Web Crypto API has been enabled by default (bug 1074001).
The MediaStreamTrack.stop() method has been added (bug 1057955).
Our experimental implementation of EME continues. The MediaKeySession.getUsableKeyIds() method has been added (bug 1057171).
Regarding WebRTC:
- an experiment implementation of RTPSender and RTPReceiver working with RTCPeerConnection has landed (bug 1032835).
- application window sharing has been added to Navigation.getUserMedia() (bug 1036653) and MediaTrackConstraintSet now supports browserWindow and scrollWithPage allowing to chose the tab of a window that has to be shared without showing the tab chooser dialog (bug 1041700).
- "browser" is now an accepted value of MediaSourceEnum, used to define constraints (bug 1041493).
For Web Components, event retargeting is now implemented (bug 887541).
The Headers interface has been implemented (bug 1029620). It is controlled by the dom.fetch.enabled preference which is set to false by default.
Regarding our experimental implementation of Web Animations, the AnimationEffect interface has been added, with the single AnimationEffect.name property (bug 1045993). Web Animations is not activated by default and is controlled by the dom.animations-api.core.enabled preference.
CSSOM View smooth scrolling methods have been added: Window.scroll(), Window.scrollTo(), and Window.scrollBy() (bug 1022818).
The non-standard MozSmsSegmentInfo is no more visible on the global object bug 916607.

MathML

No change.

SVG

No change.

Audio/Video

No change.

Security and Networking

SSLv3 is now disabled by default (bug 1030963).
A warning is sent to the console when a Web site use the CSS reflected-xss directive (bug 1045902).

Changes for add-on and Mozilla developers

localstore.rdf has been removed (bug 559505).

Add-on SDK

Highlights

New API: dev/panel enables you to extend the Firefox Developer Tools.
jpm beta released.
"./my-file" introduced everywhere as an alias for require("sdk/self").data.url("my-file")
Added the ability to attach stylesheets to individual tabs.