|Paradigm||Multi-paradigm: prototype-based, functional, imperative|
|Designed by||Brendan Eich, Ecma International|
|Typing discipline||weak, dynamic|
|SpiderMonkey, V8, ActionScript, JScript, QtScript, InScript|
|Self, HyperTalk, AWK, C, Perl, Python, Java, Scheme|
|Internet media type||
|Developed by||Sun Microsystems,
|Initial release||June 1997|
(June 17, 2015)
|Type of format||Scripting language|
|Part of a series on|
|Lists of Frameworks and Libraries|
There are six editions of ECMA-262 published. Work on version 6 of the standard, codenamed "Harmony", was finalized in June 2015.
|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 are proposed for ECMAScript Harmony.|
|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, known as ECMAScript 2015, 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, collections (maps, sets and weak maps), 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||Work in progress||The Seventh Edition is in a very early stage of development, but is intended to continue the themes of language reform, code isolation, control of effects and library/tool enabling from ES6. New features proposed include promises/concurrency, number and math enhancements, guards and trademarks (an alternative to static typing), operator overloading, value types (first-class number-like objects), new record structures (records, tuples and typed arrays), pattern matching, and traits.|
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.
As of August 2008, the ECMAScript 4th edition proposal has been scaled back into a project codenamed ECMAScript Harmony. Features under discussion for Harmony include:
- A module system
- Optional type annotations and static typing, probably using a structural type system
- Generators and iterators
- Destructuring assignment
- Algebraic data types
The intent of these features is 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.
Harmony, 6th Edition
|This section is outdated. (December 2013)|
In the July 2008 announcement, Eich also stated that the ECMAScript 4 proposal would be superseded by a new project, code-named ECMAScript Harmony. ECMAScript Harmony names the agreed upon design trajectory of post-ES5 editions. It will include syntactic extensions, but the changes will be more modest than ECMAScript 4 in both semantic and syntactic innovation. Packages, namespaces, and early binding from ECMAScript 4 are no longer included for planned releases. In addition, other goals and ideas from ECMAScript 4 are being rephrased to keep consensus in the committee; these include a notion of classes based on ECMAScript, 5th Edition (being an update to ECMAScript, 3rd edition).
|SpiderMonkey||Firefox, the Gecko layout engine, Adobe Acrobat[d 1]||ECMA-262, edition 5.1, and features from upcoming 6 and 7[d 2]|
|Rhino||Java Platform, Standard Edition|
|V8||Google Chrome, Node.js, Opera||ECMA-262, edition 5.1, and features from upcoming 6[d 3][d 4]|
|JScript 9.0||Internet Explorer, the Trident layout engine||ECMA-262, edition 5.1|
|Nashorn||Java||ECMA-262, edition 5.1[d 5]|
|Carakan (deprecated)||Opera 12||ECMA-262, edition 5[d 6][d 7]|
|RemObjects Script for .NET||ECMA-262, edition 5|
|KJS||KHTML||ECMA-262, edition 5.1[d 8] and features from upcoming 6[d 9]|
|Ejscript||Appweb Web Server, Samba 4||ECMA-262, edition 3[d 10]|
|JScript .NET||Microsoft .NET Framework||ECMA-262, edition 3[d 11]|
|ActionScript||Adobe Flash, Adobe Flex, Adobe AIR||ECMA-262, edition 4[d 12][d 13]|
|Adobe ExtendScript||Adobe Creative Suite products: InDesign, Illustrator, Photoshop,
Bridge, After Effects, Premiere Pro
|ECMA-262, edition 3|
|CriScript||ECMA-262, edition 3|
|InScript||iCab||ECMA-262, edition 3|
|Max/MSP engine||Max/MSP||ECMA-262, edition 3|
|Galio engine||Galio||ECMA-262, edition 3|
|QtScript (deprecated)||KDE SC 4||ECMA-262, edition 3|
|Caja||ECMA-262, edition 3[d 14]|
|Chakra||Microsoft Edge||ECMA-262, edition 5.1, and features from upcoming 6[d 15]|
- SpiderMonkey already supports a wide range of upcoming features: ECMAScript 6 support in Mozilla and ECMAScript 7 support in Mozilla
- Full ECMAScript 5.1 support in Opera 11.51+.
- Full ECMAScript 5.1 support in Opera 11.51+.
- "bUscher » Blog Archive » kjs finally under 1000 fails!". buschinski.de.
- Commits marked with ES6 are implementations of ES6 features: http://quickgit.kde.org/?p=kjs.git&a=shortlog
- This implementation asserts to support some extensions proposed in drafts of ECMAScript edition 4 (and now ECMAScript Harmony): Ejscript Overview.
- Microsoft asserts that JScript 8.0 supports "almost all of the features of the ECMAScript Edition 3 Language Specification", but does not list the unsupported features.
- Completely conforming implementation of the ECMAScript fourth edition draft specification: ActionScript
- In addition to supporting ECMA-262 edition 3, ActionScript 3 also included support for extensions proposed in drafts of ECMAScript edition 4: The Kiwi Project: AS3 language 101 for C/C++ coders.
- Caja emulates strict mode as specified in the ECMAScript edition 5 draft.
- Microsoft states that Edge "supports most ES2015 features," supporting 81% of the specification as of May 2015 and 67% as of September 2015. 
|1.0 (Netscape 2.0, March 1996)||1.0 (IE 3.0 – early versions, August 1996)|
|1.1 (Netscape 3.0, August 1996)||2.0 (IE 3.0 – later versions, January 1997)|
|1.2 (Netscape 4.0-4.05, June 1997)|
|1.3 (Netscape 4.06-4.7x, October 1998)||3.0 (IE 4.0, Oct 1997)||Edition 1 (June 1997) / Edition 2 (June 1998)|
|1.4 (Netscape Server only)||4.0 (Visual Studio 6, no IE release)|
|5.0 (IE 5.0, March 1999)|
|5.1 (IE 5.01)|
|1.5 (Netscape 6.0, Nov 2000; also
later Netscape and Mozilla releases)
|5.5 (IE 5.5, July 2000)||Edition 3 (December 1999)|
|5.6 (IE 6.0, October 2001)|
|JScript .NET (ASP.NET; no IE release)||(JScript .NET is said to have been designed with the participation of other Ecma members)|
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[update].
The following table shows current conformance results of browser products. Lower scores are better, although scores can not be compared, as tests are not weighted. Also, be aware that Test262 itself is likely to contain bugs that may impact a browser's score. So browsers with a score significantly lower than the current test suite bug count may not necessarily do better than those with a higher one. That may be particularly true when several browsers have a higher score in their current development builds as compared to their last released version.
|Product||Latest Stable||Test262 failed||Preview/Beta||Test262 failed||Alpha||Test262 failed||Nightly||Test262 failed|
|Google Chrome||46.0.2490.86 m||207/11552||47.0.2526.69 beta-m||208/11552||48.0.2564.10 dev-m||203/11552||48.0.2569.0 canary||203/11552|
|Mozilla Firefox||42.0||260/11552||43.0 Beta 5||260/11552||44.0a2 (20151120004044)||260/11552||45.0a1 (20151120030227)||260/11552|
|Internet Explorer||11.0.25 (11.0.9600.18097)||8/11552|
|Opera||33.0.1990.115||207/11552||beta 34.0.2036.3||208/11552||developer 35.0.2052.0||210/11552|
- Comparison of layout engines (ECMAScript)
- Dart (programming language)
- Document Object Model (DOM)
- ECMAScript for XML (E4X)
- List of ECMAScript engines
- Qt Meta (or Modeling) Language (QML)
- "TC39 - ECMAScript® (formerly TC39-TG1)". ecma-international.org. Ecma International. Retrieved 22 August 2015.
- "Press Release". Web.archive.org. Archived from the original on 2007-09-16. Retrieved 2013-10-31.
- "Brendan's Roadmap Updates: Popularity". weblogs.mozillazine.org. Archived from the original on 17 May 2008.
- "Press Release". Web.archive.org. Archived from the original on 1998-12-03. Retrieved 2013-10-31.
- "Will there be a suggested file suffix for es4?". Mail.mozilla.org. 2006-10-03. Retrieved 2013-10-31.
- . EMCAScript. Retrieved on 2015-06-19.
- "strawman:strawman [ES Wiki]". Wiki.ecmascript.org. 2013-09-18. Retrieved 2013-10-31.
- 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.
- "Compatibility Between ES3 and Proposed ES4" (PDF). Ecmascript.org. Retrieved 2013-10-31.
- "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.
- John Resig. "John Resig – ECMAScript Harmony". Ejohn.org. Retrieved 2013-10-31.
- harmony:specification_drafts [ES Wiki]. Wiki.ecmascript.org. Retrieved on 2013-10-23.
- "About". ECMAScript. Retrieved 2009-12-17.
- "Version Information (JScript)". Msdn.microsoft.com. Archived from the original on 2009-12-17. Retrieved 2009-12-17.
- "Introducing JScript .NET". Microsoft.com. Retrieved 2010-01-12.
- "ECMAScript Language – test262". Test262.ecmascript.org. Retrieved 2013-10-31.
- Schuster, Tom. "Bug 1453". ecmascript.org bug database. Retrieved 12 October 2014.
- 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)