|Paradigm||Multi-paradigm: prototype-based, functional, imperative|
|Designed by||Brendan Eich, Ecma International|
|Typing discipline||weak, dynamic|
|Self, HyperTalk, AWK, C, Perl, Python, Java, Scheme|
|Internet media type||
|Initial release||June 1997|
(June 2018 )
|Type of format||Scripting language|
|Part of a series on|
|Lists of Frameworks and Libraries|
|Edition||Date published||Changes from prior edition||Editor|
|1||June 1997||First edition||Guy L. Steele Jr.|
|2||June 1998||Editorial changes to keep the specification fully aligned with ISO/IEC 16262 international standard||Mike Cowlishaw|
|3||December 1999||Added regular expressions, better string handling, new control statements, try/catch exception handling, tighter definition of errors, formatting for numeric output and other enhancements||Mike Cowlishaw|
|4||Abandoned||Fourth Edition was abandoned, due to political differences concerning language complexity. Many features proposed for the Fourth Edition have been completely dropped; some were incorporated into the sixth edition.|
|5||December 2009||Adds "strict mode," a subset intended to provide more thorough error checking and avoid error-prone constructs. Clarifies many ambiguities in the 3rd edition specification, and accommodates behaviour of real-world implementations that differed consistently from that specification. Adds some new features, such as getters and setters, library support for JSON, and more complete reflection on object properties.||Pratap Lakshman, Allen Wirfs-Brock|
|5.1||June 2011||This edition 5.1 of the ECMAScript standard is fully aligned with third edition of the international standard ISO/IEC 16262:2011.||Pratap Lakshman, Allen Wirfs-Brock|
|6||June 2015||The sixth edition, initially known as ECMAScript 6 (ES6) and later renamed to ECMAScript 2015 (ES2015) adds significant new syntax for writing complex applications, including classes and modules, but defines them semantically in the same terms as ECMAScript 5 strict mode. Other new features include iterators and for/of loops, Python-style generators and generator expressions, arrow functions, binary data, typed arrays, collections (maps, sets and weak maps), promises, number and math enhancements, reflection, and proxies (metaprogramming for virtual objects and wrappers). As the first "ECMAScript Harmony" specification, it is also known as "ES6 Harmony."||Allen Wirfs-Brock|
|7||June 2016||ECMAScript 2016 (ES2016), the seventh edition, intended to continue the themes of language reform, code isolation, control of effects and library/tool enabling from ES2015, includes two new features: the exponentiation operator (
|8||June 2017||ECMAScript 2017 (ES2017), the eighth edition, includes features for concurrency and atomics, syntactic integration with promises (async/await).||Brian Terlson|
|9||June 2018||ECMAScript 2018 (ES2018), the ninth edition, includes features for asynchronous iteration and generators, new regular expression features and rest/spread parameters.||Brian Terlson|
In June 2004, Ecma International published ECMA-357 standard, defining an extension to ECMAScript, known as ECMAScript for XML (E4X). Ecma also defined a "Compact Profile" for ECMAScript – known as ES-CP, or ECMA 327 – that was designed for resource-constrained devices, which was withdrawn in 2015.
4th Edition (abandoned)
The proposed fourth edition of ECMA-262 (ECMAScript 4 or ES4) would have been the first major update to ECMAScript since the third edition was published in 1999. The specification (along with a reference implementation) was originally targeted for completion by October 2008. An overview of the language was released by the working group on October 23, 2007.
By August 2008, the ECMAScript 4th edition proposal had been scaled back into a project codenamed ECMAScript Harmony. Features under discussion for Harmony at the time included
- a module system,
- optional type annotations and static typing, probably using a structural type system,
- generators and iterators,
- destructuring assignment, and
- algebraic data types.
Intent of these features was partly to better support programming in the large, and to allow sacrificing some of the script's ability to be dynamic to improve performance. For example, Tamarin – the virtual machine for ActionScript, developed and open sourced by Adobe – has just-in-time compilation (JIT) support for certain classes of scripts.
In addition to introducing new features, some ES3 bugs were proposed to be fixed in edition 4. These fixes and others, and support for JSON encoding/decoding, have been folded into the ECMAScript, 5th Edition specification.
Yahoo, Microsoft, Google, and other 4th edition dissenters formed their own subcommittee to design a less ambitious update of ECMAScript 3, tentatively named ECMAScript 3.1. This edition would focus on security and library updates with a large emphasis on compatibility. After the aforementioned public sparring, the ECMAScript 3.1 and ECMAScript 4 teams agreed on a compromise: the two editions would be worked on, in parallel, with coordination between the teams to ensure that ECMAScript 3.1 remains a strict subset of ECMAScript 4 in both semantics and syntax.
However, the differing philosophies in each team resulted in repeated breakages of the subset rule, and it remained doubtful that the ECMAScript 4 dissenters would ever support or implement ECMAScript 4 in the future. After over a year since the disagreement over the future of ECMAScript within the Ecma Technical Committee 39, the two teams reached a new compromise in July 2008: Brendan Eich announced that Ecma TC39 would focus work on the ECMAScript 3.1 (later renamed to ECMAScript, 5th Edition) project with full collaboration of all parties, and vendors would target at least two interoperable implementations by early 2009. In April 2009, Ecma TC39 published the "final" draft of the 5th edition and announced that testing of interoperable implementations was expected to be completed by mid-July. On December 3, 2009, ECMA-262 5th edition was published.
6th Edition - ECMAScript 2015
The 6th edition, officially known as ECMAScript 2015, was finalized in June 2015. This update adds significant new syntax for writing complex applications, including classes and modules, but defines them semantically in the same terms as ECMAScript 5 strict mode. Other new features include iterators and for/of loops, Python-style generators, arrow functions, binary data, typed arrays, collections (maps, sets and weak maps), promises, number and math enhancements, reflection, and proxies (metaprogramming for virtual objects and wrappers). The complete list is extensive.
7th Edition - ECMAScript 2016
The 7th edition, officially known as ECMAScript 2016, was finalized in June 2016. New features include the exponentiation operator (**), Array.prototype.includes (not to be confused with ClassList.contains).
8th Edition - ECMAScript 2017
The 8th edition, officially known as ECMAScript 2017, was finalized in June 2017. Includes async/await, which works using generators and promises.
9th Edition - ECMAScript 2018
The 9th edition, officially known as ECMAScript 2018, was finalized in June 2018. New features include rest/spread properties, asynchronous iteration, Promise.prototype.finally() and additions to RegExp.
ES.Next is a dynamic name that refers to whatever the next version is at time of writing. ES.Next features are more correctly called proposals, because, by definition, the specification has not been finalized yet.
Development of test262 is a project of Ecma Technical Committee 39 (TC39). The testing framework and individual tests are created by member organizations of TC39 and contributed to Ecma for use in Test262.
Important contributions were made by Google (Sputnik testsuite) and Microsoft who both contributed thousands of tests. The Test262 testsuite already contains more than 11,000 tests and is being developed further as of 2013.
ECMAScript specifications through ES7 are well-supported in major web browsers. The table below shows the conformance rate for current versions of software with respect to the most recent editions of ECMAScript.
|Scripting engine||Reference application(s)||Conformance|
|Chrome V8||Google Chrome, Opera||100%||98%||100%||93%|
- "TC39 - ECMAScript® (formerly TC39-TG1)". ecma-international.org. Ecma International. Retrieved 22 August 2015.
- "Will there be a suggested file suffix for es4?". Mail.mozilla.org. 2006-10-03. Retrieved 2013-10-31.
- "ECMAScript 2018 Language Specification". Ecma International. June 2018.
- "ECMAScript 2015 Language Specification". Ecma International. June 2015.
- "ECMAScript 2016 Language Specification". Ecma International. June 2016.
- "ECMAScript 2017 Language Specification". Ecma International. June 2017.
- "ECMAScript 2017 (ES8): the final feature set". 2ality. Retrieved 2018-04-23.
- 2015-03-24 Meeting Notes. ESDiscuss. Also see Ecma withdrawn Standards. ECMA.
- "ES4 overview paper released". Mail.mozilla.org. Retrieved 2013-10-31.
- "Proposed ECMAScript 4th Edition – Language Overview" (PDF). ecmascript.org. 23 October 2007. Archived from the original (PDF) on 13 July 2010.
- "Compatibility Between ES3 and Proposed ES4" (PDF). Ecmascript.org. Retrieved 2013-10-31.
- "Wayback Machine" (PDF). 2009-04-19. Retrieved 2018-03-19.
- "ECMAScript 3 and Beyond – IEBlog – Site Home – MSDN Blogs". Blogs.msdn.com. 2007-10-30. Retrieved 2013-10-31.
- "What I think about ES4. - Albatross! - Site Home – MSDN Blogs". Blogs.msdn.com. 2007-10-31. Retrieved 2013-10-31.
- "Open letter to Chris Wilson". Brendan Eich. 2007-10-31. Retrieved 2013-10-31.
- "ECMAScript Harmony". Mail.mozilla.org. Retrieved 2013-10-31.
- "Ecma International finalises major revision of ECMAScript". Ecma International. 2009-04-09. Retrieved 2009-05-22.
- "Ecma latest news". Ecma-international.org. Retrieved 2013-10-31.
- Krill, Paul. "It's official: ECMAScript 6 is approved". InfoWorld. Retrieved 2018-03-19.
- "5 Great Features in EcmaScript 6 (ES6 Harmony) - Wintellect". Wintellect. 2014-03-24. Retrieved 2018-03-19.
- "ECMAScript 6: New Features: Overview and Comparison". es6-features.org. Retrieved 2018-03-19.
- "About". ECMAScript. Archived from the original on 2012-08-02. Retrieved 2009-12-17.
- "Using ES2015 today". Wisdom Geek. 2016-05-12. Retrieved 2018-08-29.
- "ECMAScript Language – test262". Test262.ecmascript.org. Archived from the original on 2011-05-14. Retrieved 2013-10-31.
- ES5 is the baseline for this test suite. The conformance rate for other editions reflects support for new features only, not a comprehensive score.
- "ECMAScript 5 compatibility table". kangax.github.io. Retrieved 2018-03-19.
- "ECMAScript 6 compatibility table". kangax.github.io. Retrieved 2018-03-19.
- "ECMAScript 2016+ compatibility table". kangax.github.io. Retrieved 2018-03-19.
- Composite score that includes new features from ES7 through next edition drafts
- ISO Standard
- Ecma Standards
- ECMA-290 ECMAScript Components Specification (June 1999)
- ECMA-327 ECMAScript 3rd Edition Compact Profile (June 2001)
- ECMA-357 ECMAScript for XML (E4X) Specification (June 2004)