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ECMAScript 2015 support in Mozilla

ECMAScript 2015 is the sixth edition of the ECMAScript Language Specification standard. It defines the standard for the JavaScript implementation in SpiderMonkey, the engine used in Firefox and other Mozilla applications.

Code-named "", "Harmony", or "ECMAScript 6", the first working draft (based on ECMAScript 5.1) was published on July 12, 2011 as "". In August 2014, the ECMAScript 2015 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

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

Standard library

Additions to the Array object

New Map and Set objects, and their weak counterparts

New Math functions

Additions to the Number object

Additions to the Object object

Additions to the Date object

New Promise object

New Proxy object

New Reflect object

Additions to the RegExp object

Additions to the String object

New Symbol object

Typed Arrays

Typed arrays are specified as part of ECMAScript 2015 and no longer in their own specification.

Expressions and operators



Other features

See also