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|Paradigm||Multi-paradigm: prototype-based, functional, imperative, scripting|
|Designed by||Brendan Eich, Ecma International|
|Typing discipline||duck, weak, dynamic|
|Influenced by||Self, HyperTalk, AWK, C, Perl, Python, Java|
| This article is part of
There are four editions of ECMA-262 published. Work on a future edition codenamed "Harmony", is in progress.
|Edition||Date published||Differences to the previous 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, with some of the work forming the basis of Fifth Edition and some forming the basis of 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|
|Harmony||Work in progress||Multiple new concepts and language features — see the section "Future development" below.|
In June 2004, Ecma International published ECMA-357 standard, defining an extension to ECMAScript, known as E4X (ECMAScript for XML).
Ecma also defined a "Compact Profile" for ECMAScript — known as ES-CP, or ECMA 327 — which is designed for resource-constrained devices. Several of the dynamic features of ECMAScript (such as the "eval" function) are made optional, thus allowing the runtime to make more assumptions about the behaviour of programs and therefore make more performance trade-offs when running the code. The HD DVD standard was one place where the ECMAScript Compact Profile was used in favour of full ECMAScript in order to reduce processing and memory requirements on a device.
Note that there is a distinction between a dialect and an implementation. A dialect of a language is significant variation of the language, while an implementation of a language/dialect executes a program written in that dialect.
|Application/Implementation||Dialect and latest version||ECMAScript edition|
|Internet Explorer, the Trident layout engine||JScript 5.8||ECMA-262, edition 3|
|Opera||ECMAScript[d 4]||ECMA-262, edition 3|
|Appweb Web Server, Samba 4||Ejscript 0.9.9||ECMA-262, edition 3[d 6]|
|Microsoft .NET Framework||JScript .NET 8.0||ECMA-262, edition 3[d 7]|
|Adobe Flash and Adobe Flex||ActionScript 3||ECMA-262, edition 3[d 8]|
|General purpose scripting language||DMDScript 1.15||ECMA-262|
|CriScript, JScript for game platforms||CriScript 0.91.0||ECMA-262, edition 3|
|iCab||InScript 3.22 (abandoned)||ECMA-262, edition 3|
|KDE||QtScript||ECMA-262, edition 3|
|Caja||ECMA-262, edition 3[d 13]|
|Objective-J||ECMA-262, edition 3|
|WMLScript||ECMA-262, edition 3|
- ↑ 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.
- ↑ 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.
- ↑ As of version 4, OpenLaszlo implements standard ECMAScript edition 3 with some extensions proposed in drafts of ECMAScript edition 4: OpenLaszlo 4.
- ↑ Caja emulates strict mode as specified in the ECMAScript edition 5 draft.
|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)|
|1.6 (Gecko 1.8, Firefox 1.5, November 2005)||Edition 3, with some compliant enhancements: E4X, |
|JScript .NET (ASP.NET; no IE release)||(JScript .NET is said to have been designed with the participation of other Ecma members)|
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 22, 2007.
As of August 2008, the ECMAScript 4th edition proposal has been scaled back into a project codenamed ECMAScript Harmony.
Features under discussion for a future edition (originally "ECMAScript 4"; now ECMAScript 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 let programmers sacrifice some of the script's ability to be dynamic for performance. For example, Tamarin — the virtual machine for ActionScript developed and open sourced by Adobe — has JIT compilation support for certain classes of scripts.
Bug fixes and backwards compatibility
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.
The update has not been without controversy. In late 2007, a debate between Eich, now the Mozilla Foundation's CTO, and Chris Wilson, Microsoft's platform architect for Internet Explorer, became public on a number of blogs. Wilson cautioned that because the proposed changes to ECMAScript made it backwards incompatible in some respects to earlier versions of the language, the update amounted to "breaking the Web," and that stakeholders who opposed the changes were being "hidden from view". Eich responded by stating that Wilson seemed to be "repeating falsehoods in blogs" and denied that there was attempt to suppress dissent and challenging critics to give specific examples of incompatibility. He also pointed out that Microsoft Silverlight and Adobe AIR rely on C# and ActionScript 3 respectively, both of which are larger and more complex than ECMAScript Edition 3.
ECMAScript, 5th Edition
Microsoft, Yahoo, 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 August 2008: Ecma TC39 announced it would focus work on the ECMAScript 3.1 (later renamed to ECMAScript, 5th Edition) project with full collaboration of all parties, and it would target 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.
In the same announcement, Ecma TC39 also stated that the ECMAScript 4 proposal would be superseded by a new project, code-named ECMAScript Harmony. ECMAScript Harmony 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). As of December 2009, there is no publicly announced release date for ECMAScript Harmony. Depending on Ecma, Harmony may end up being called ECMAScript, 6th edition.
- Comparison of layout engines (ECMAScript)
- Document Object Model
- List of ECMAScript engines
- ↑ RFC 4329
- ↑ Brendan's Roadmap Updates: Popularity
- ↑ ECMAScript 3rd Edition specification
- ↑ es4-discuss: Will there be a suggested file suffix for es4?
- ↑ "About". ECMAScript. http://www.ecmascript.org/about.php. Retrieved 2009-12-17.
- ↑ "Version Information (JScript)". Msdn.microsoft.com. http://msdn.microsoft.com/library/default.asp?url=/library/en-us/script56/html/js56jsoriversioninformation.asp. Retrieved 2009-12-17.
- ↑ "Introducing JScript .NET". Microsoft.com. http://msdn.microsoft.com/en-us/library/ms974588.aspx#scripting0714_topic4. Retrieved 2010-01-12.
- ↑ es4-discuss: ES4 overview paper released
- ↑ Incompatibilities between ES3 and ES4
- ↑ [dead link]
- ↑ IEBlog: ECMAScript 3 and Beyond
- ↑ Albatross!: What I think about ES4
- ↑ Brendan's Roadmap Updates: Open letter to Chris Wilson
- ↑ Brendan's Roadmap Updates: My @media Ajax Keynote
- ↑ ECMAScript Harmony announcement
- ↑ Announcement of the 5th edition candidate by the specification editors
- ↑ "Ecma International finalises major revision of ECMAScript". Ecma International. 2009-04-09. http://www.ecma-international.org/news/PressReleases/PR_Ecma_finalises_major_revision_of_ECMAScript.htm. Retrieved 2009-05-22.
- ↑ Ecma News: 98th General Assembly approved documents
- ↑ John Resig: ECMAScript Harmony
- ECMAScript Official Website
- 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)
- The World of ECMAScript : John Resig's map on ECMAScript
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