Mozilla对ECMAScript 6的支持

ECMAScript 2015 (6th Edition)是目前ECMAScript语言规范的标准。通常被称为"ES6"，it defines the standard for the JavaScript implementation in SpiderMonkey, the engine used in Firefox and other Mozilla applications.

Code-named "ES.next" or "Harmony", the first working draft (based on ECMAScript 5.1) was published on July 12, 2011 as "ES.next". In August 2014, the ECMAScript 6 draft specification was feature frozen and went through a stabilization and bug fixing period. Finally, ECMA-262 Edition 6 got officially approved and published as a standard on June 17, 2015 by the ECMA General Assembly. It will also appear as the international industry standard ISO/IEC 16262:2016.

A PDF and HTML version of the standard can be freely downloaded on ecma-international.org.

A channel for feedback on ECMAScript standards is es-discuss.

Firefox 已经支持的 ECMAScript 6 特性

这里列出的功能已经在Firefox中支持；the version in which support was added is also indicated for each feature.

标准库

Additions to the Array object

• Array iteration with for...of (Firefox 13)
• Array.from() (Firefox 32)
• Array.of() (Firefox 25)
• Array.prototype.fill() (Firefox 31)
• Array.prototype.find(), Array.prototype.findIndex() (Firefox 25)
• Array.prototype.entries(),
  Array.prototype.keys() (Firefox 28)
• Array.prototype.copyWithin() (Firefox 32)

新的Map和Set，以及WeakMap和WeakSet对象

• Map (Firefox 13)
  • Map iteration with for...of (Firefox 17)
  • Map.prototype.forEach() (Firefox 25)
  • Map.prototype.entries(),
    Map.prototype.keys(),
    Map.prototype.values() (Firefox 20)
  • Constructor argument: new Map(null) (Firefox 37)
  • Monkey-patched set() in Constructor (Firefox 37)
  • get Map[@@species] (Firefox 41)
• Set (Firefox 13)
  • Set iteration with for...of (Firefox 17)
  • Set.prototype.forEach() (Firefox 25)
  • Set.prototype.entries(),
    Set.prototype.keys(),
    Set.prototype.values() (Firefox 24)
  • Constructor argument: new Set(null) (Firefox 37)
  • Monkey-patched add() in Constructor (Firefox 37)
  • get Set[@@species] (Firefox 41)
• WeakMap (Firefox 6)
  • WeakMap.clear() (Firefox 20)
  • optional iterable argument in WeakMap constructor (Firefox 36)
  • Constructor argument: new WeakMap(null) (Firefox 37)
  • Monkey-patched set() in Constructor (Firefox 37)
• WeakSet (Firefox 34)
  • Constructor argument: new WeakSet(null) (Firefox 37)
  • Monkey-patched add() in Constructor (Firefox 37)

新的Math函数

• Math.imul() (Firefox 20)
• Math.clz32() (Firefox 31)
• Math.fround() (Firefox 26)
• Math.log10(), Math.log2(), Math.log1p(), Math.expm1(), Math.cosh(), Math.sinh(), Math.tanh(), Math.acosh(), Math.asinh(), Math.atanh(), Math.hypot(), Math.trunc(), Math.sign(), Math.cbrt() (Firefox 25)

Additions to the Number object

• Number.isNaN() (Firefox 16)
• Number.isFinite() (Firefox 16)
• Number.isInteger() (Firefox 16)
• Number.parseInt() (Firefox 25)
• Number.parseFloat() (Firefox 25)
• Number.EPSILON (Firefox 25)
• Number.MAX_SAFE_INTEGER, Number.MIN_SAFE_INTEGER (Firefox 31)
• Number.isSafeInteger() (Firefox 32)

Additions to the Object object

• Object.prototype.__proto__ has been standardized
• Object.is() (Firefox 22)
• Object.setPrototypeOf() (Firefox 31)
• Object.assign() (Firefox 34)
• Object.getOwnPropertySymbols() (Firefox 33)

Additions to the Date object

• Date.prototype is an ordinary object (Firefox 41)
• generic Date.prototype.toString (Firefox 41)

新的Promise对象

• Promise (Firefox 24, enabled by default in Firefox 29)

新的Reflect对象

• Reflect (Firefox 42)

Additions to the RegExp object

• RegExp sticky (y) flag (Firefox 3)
• generic RegExp.prototype.toString (Firefox 39)

Additions to the String object

• String.fromCodePoint() (Firefox 29)
• String.prototype.codePointAt() (Firefox 29)
• String.prototype.startsWith(), String.prototype.endsWith() (Firefox 17)
• String.prototype.includes() (Firefox 40) (formerly String.prototype.contains() (Firefox 17))
• String.prototype.repeat() (Firefox 24)
• String.prototype.normalize() (Firefox 31)
• String.raw() (Firefox 34)
• \u{XXXXXX} Unicode code point escapes (Firefox 40)

新的Symbol对象

• Symbol (Firefox 36)
• Symbol.iterator (Firefox 36)
• Symbol.for() - global Symbol registry (Firefox 36)
• Symbol.match (Firefox 40)
• Symbol.species (Firefox 41)

Typed Arrays

Typed arrays are specified as part of ECMAScript 6 and no longer in their own specification.

• ArrayBuffer
• DataView
• Int8Array
• Uint8Array
• Uint8ClampedArray
• Int16Array
• Uint16Array
• Int32Array
• Uint32Array
• Float32Array
• Float64Array

表达式和操作符

• Spread operator for arrays (Firefox 16)
  • use Symbol.iterator property (Firefox 36)
• Spread operator for function calls (Firefox 27)
  • use Symbol.iterator property (Firefox 36)

语句和声明

• for...of (Firefox 13)
  • works in terms of .iterator() and .next() (Firefox 17)
  • use "@@iterator" property (Firefox 27)
  • use Symbol.iterator property (Firefox 36)

函数

• Rest parameters (Firefox 15)
• Default parameters (Firefox 15)
  • Parameters without defaults after default parameters (Firefox 26)
  • Destructured parameters with default value assignment (Firefox 41)
• Arrow functions (Firefox 22)
• Generator function (Firefox 26)
  • yield (Firefox 26)
  • yield* (Firefox 27)

其他特性

• Binary and octal numeric literals (Firefox 25)
• Template strings (Firefox 34)
• Object initializer: shorthand property names (Firefox 33)
• Object initializer: computed property names (Firefox 34)
• Object initializer: shorthand method names (Firefox 34)

和ES6规范不兼容的特性

The following features are (partially) implemented in Firefox, but are not compliant with the specification. There are a couple of possible reasons for this: Firefox's implementation is based on an older draft of the ES6 specification, or Firefox's current implementation is an experimental design added before a similar feature was added to the ES6 specification.

• Legacy iterators and generators (JS 1.7, Firefox 2)
  • ES6 iterators and generators implemented in Firefox 26+
• Destructuring assignment (JS 1.7, Firefox 2) (ES6 compliance bug 950547)
• const (JS 1.5, Firefox 1.0) (ES6 compliance bug 950547)
• let (JS 1.7, Firefox 2) (ES6 compliance bug 950547)
• Proxy (Firefox 18) (ES6 compliance bug 978228)

Features partially supported by Firefox

These features, while part of ECMAScript 6, are only partially implemented in Firefox, and are only available in nightly builds.

New class syntax

• Basic support (bug 837314)
• extends support
• static method definitions

Firefox还未支持的 ECMAScript 6 特性

The following features are part of the ECMAScript 6 specification, but haven't been implemented yet in Firefox. The bug tracking implementation of the feature is noted for each.

• Modules (bug 568953)
  • import syntax
  • export syntax
• Array.prototype.values() (bug 875433)
• Well-known symbols (bug 1119779)
• RegExp "u" flag (bug 1135377)

相关链接

• ECMAScript 6规范草案
• Mozilla ES6 tracking bug
• 支持ECMAScript 6的浏览器