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ECMAScript

ECMAScript
Paradigm(s)Multi-paradigm: prototype-based, functional, imperative, scripting
Appeared in1997
Designed byBrendan Eich, Ecma International
Typing disciplineDuck, weak, dynamic
DialectsJavaScript, ActionScript, JScript, QML, QtScript, InScript
Influenced bySelf, HyperTalk, AWK, C, Perl, Python, Java, Scheme
ECMAScript
Crystal source.png
Filename extension.es
Internet media typeapplication/ecmascript[1]
Developed bySun Microsystems,
Ecma International
Initial releaseJune 1997
Latest releaseEdition 5.1 / June 2011; 21 months ago (June 2011)
Type of formatScripting language
Extended fromJavaScript
WebsiteECMA-262, ECMA-290,
ECMA-327, ECMA-357
Part of a series on
JavaScript

ECMAScript is the scripting language standardized by Ecma International in the ECMA-262 specification and ISO/IEC 16262. The language is widely used for client-side scripting on the web, in the form of several well-known dialects such as JavaScript, JScript and ActionScript.

Contents

History

JavaScript was originally developed by Brendan Eich of Netscape under the name Mocha, later LiveScript, and finally renamed to JavaScript.[2] In December 1995, Sun Microsystems and Netscape announced JavaScript in a press release.[3] In March 1996, Netscape Navigator 2.0 was released, featuring support for JavaScript.

Due to the widespread success of JavaScript as a client-side scripting language for web pages, Microsoft developed a compatible dialect of the language, naming it JScript to avoid trademark issues. JScript added new date methods to fix the non-Y2K-friendly methods in JavaScript, which were based on the Java Date class.[4] JScript was included in Internet Explorer 3.0, released in August 1996.

Netscape delivered JavaScript to Ecma International for standardization and the work on the specification, ECMA-262, began in November 1996.[5] The first edition of ECMA-262 was adopted by the Ecma General Assembly of June 1997. Several editions of the language standard have been published since then.

ECMAScript is the name of the scripting language standardized in ECMA-262. The name "ECMAScript" was a compromise between the organizations involved in standardizing the language, especially Netscape and Microsoft, whose disputes dominated the early standards sessions. Brendan Eich, the creator of JavaScript, commented that "ECMAScript was always an unwanted trade name that sounds like a skin disease."[6]

While both JavaScript and JScript aim to be compatible with ECMAScript, they also provide additional features not described in the ECMA specifications.[citation needed]

Versions

There are five editions of ECMA-262 published. Work on a future edition, codenamed "Harmony", is in progress.[7]

EditionDate publishedChanges from prior editionEditor
1June 1997First editionGuy L. Steele, Jr.
2June 1998Editorial changes to keep the specification fully aligned with ISO/IEC 16262 international standardMike Cowlishaw
3December 1999Added regular expressions, better string handling, new control statements, try/catch exception handling, tighter definition of errors, formatting for numeric output and other enhancementsMike Cowlishaw
4AbandonedFourth 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. 
5December 2009Adds "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.[8]Pratap Lakshman, Allen Wirfs-Brock
5.1June 2011This edition 5.1 of the ECMAScript Standard is fully aligned with third edition of the international standard ISO/IEC 16262:2011Pratap Lakshman, Allen Wirfs-Brock
HarmonyWork in progress.Version 6 is rumored to have support for classes, a concept long supported by languages like Java, C++ and C#, in addition to multiple new concepts and language features. 

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 — 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 to reduce processing and memory needs on devices.

Features

Further information: ECMAScript features

The ECMAScript language includes structured, dynamic, functional, and prototype-based features, as officially summarized here.[9]

Syntax

Further information: ECMAScript syntax

Dialects

ECMAScript is supported in many applications, especially web browsers, where it is implemented by JavaScript, or, in the case of Internet Explorer, JScript. Dialects sometimes include extensions to the language, or to the standard library and related application programming interfaces (API) such as the World Wide Web Consortium (W3C) specified Document Object Model (DOM). This means that applications written in one dialect may be incompatible with another, unless they are written to use only a common subset of supported features and APIs.

Application-implementationDialect and latest versionECMAScript edition
Mozilla Firefox, the Gecko layout engine, SpiderMonkey, and Rhino[d 1]JavaScript 1.8.5[d 2]ECMA-262, edition 5
Google Chrome, the V8 engineJavaScript[d 2]ECMA-262, edition 5[d 3][d 4]
Internet Explorer, the Trident layout engineJScript 9.0ECMA-262, edition 5
OperaECMAScript[d 5]ECMA-262, edition 5[d 6]
RemObjects Script for .NETECMAScriptECMA-262, edition 5
KHTML layout engine, KDE's Konqueror, and Apple Inc.'s Safari[d 7]JavaScript[d 2]ECMA-262, edition 3
Appweb Web Server, Samba 4Ejscript 0.9.9ECMA-262, edition 3[d 8]
Microsoft .NET FrameworkJScript .NET 8.0ECMA-262, edition 3[d 9]
Adobe Flash and Adobe FlexActionScript 3ECMA-262, edition 3[d 10]
Adobe AcrobatJavaScript 1.7[d 11]ECMA-262, edition 3
Adobe Creative Suite products: InDesign, Illustrator,

Photoshop, Bridge, After Effects, Premiere Pro

ExtendScriptECMA-262, edition 3[citation needed]
General purpose scripting languageDMDScript 1.15ECMA-262
OpenLaszloJavaScript[d 12]ECMA-262, edition 3[d 13]
CriScript, JScript for game platformsCriScript 0.91.0ECMA-262, edition 3
iCabInScript 3.22 (abandoned)ECMA-262, edition 3
Max/MSPJavaScript 1.5[d 2]ECMA-262, edition 3
ANT Galio 3JavaScript 1.5[d 2][d 14]ECMA-262, edition 3
KDEQtScriptECMA-262, edition 3
 CajaECMA-262, edition 3[d 15]
 Objective-JECMA-262, edition 3
 WMLScriptECMA-262, edition 3
JavaScriptTypeScript[10]ECMA-262, edition 3, 5 and features from upcoming 6.
  1. ^ The Mozilla implementations, (SpiderMonkey in the C++ language, Rhino in the Java language), are used in several third-party programs, including the Yahoo! Widget Engine (Konfabulator) and the Macintosh system-level scripting language JavaScript OSA.
  2. ^ a b c d e "JavaScript" is an ECMAScript variant managed by Mozilla. All non-Mozilla implementations using JavaScript are actually implementing ECMAScript, rather than Javascript. "JavaScript" support generally is meant to describe support for ECMA-262, edition 3, though some—notably Chrome, but also Opera 12 and Internet Explorer 10—target ECMA-262, edition 5.
  3. ^ V8, the JavaScript engine created by Google and used in Chrome, implements ECMAScript as specified in ECMA-262, 5th edition: V8 JavaScript Engine.
  4. ^ Chrome also implements non-ECMAScript-standard extensions to the language which are present in WebKit, in order to maintain compatibility with JavaScriptCore (which is itself based on the KDE KJS library) : V8 JavaScript Engine issue tracker.
  5. ^ Opera's implementation includes some JavaScript and JScript extensions: ECMAScript support in Opera Presto 2.3
  6. ^ Full ECMAScript (JavaScript) 5.1 support in Opera 11.51+ : [1].
  7. ^ Apple's Safari uses JavaScriptCore which is based on the KDE KJS library.
  8. ^ This implementation asserts to support some extensions proposed in drafts of ECMAScript edition 4 (and now ECMAScript Harmony): Ejscript Overview.
  9. ^ 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.
  10. ^ 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.
  11. ^ Adobe Acrobat 9.0 uses the SpiderMonkey 1.7 engine: JavaScript for Acrobat API Reference
  12. ^ OpenLaszlo both uses an ECMAScript dialect as noted in the Developer's Guide: Appendix B: ECMAScript and can compile down to JavaScript targeted for the browser (the DHTML target).
  13. ^ As of version 4, OpenLaszlo implements standard ECMAScript edition 3 with some extensions proposed in drafts of ECMAScript edition 4: OpenLaszlo 4.
  14. ^ ANT Galio Browser claims support for JavaScript 1.5.
  15. ^ Caja emulates strict mode as specified in the ECMAScript edition 5 draft.

Version correspondence

The following table is based on tedster's history compilation forum post[11] and Microsoft's JScript version information webpage.[12] Items on the same line are approximately the same language.

JavaScriptJScriptECMAScript
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: ECMAScript for XML (E4X), Array extras (e.g. Array.prototype.forEach), Array and String generics (New in JavaScript 1.6)
1.7 (Gecko 1.8.1, Firefox 2, October 2006) Edition 3 plus all JavaScript 1.6 enhancements, plus Pythonic generators and array comprehensions ([a*a for (a in iter)]), block scope with let, destructuring assignment (var [a,b]=[1,2]) (New in JavaScript 1.7)
1.8 (Gecko 1.9, Firefox 3, June 2008) Edition 3 plus all JavaScript 1.7 enhancements, plus expression closures (function(x) x * x), generator expressions, and more (New in JavaScript 1.8)
 JScript .NET (ASP.NET; no IE release)(JScript .NET is said to have been designed with the participation of other Ecma members)[13]
JavaScript 2.0 (Work in progress) Harmony (Work in progress; see the section "ECMAScript Harmony" below).

Conformance tests

In 2010, Ecma International started developing a standards test for Ecma 262 ECMAScript. Test262 is an ECMAScript conformance test suite that can be used to check how closely a JavaScript implementation follows the ECMAScript 5th Edition Specification. The test suite contains thousands of individual tests, each of which tests some specific requirements of the ECMAScript specification.

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 2012[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.

ProductCurrent versionTest262 failedTest suite version (date)Pre-release versionTest262 failedTest suite version (date)
Safari6.0.2 (8536.26.17)70007000000000000007/11572ES5.1 (2012-12-17)   
Internet Explorer10.0 (10.0.9200.16521)70008000000000000008/11573ES5.1 (2013-02-07)   
Chrome24.0.1312.57 m700114000000000000014/11572ES5.1 (2012-12-17)27.0.1423.0 dev70009000000000000009/11573ES5.1 (2013-2-07)
Opera12.14 (build 1738)700110000000000000010/11573ES5.1 (2013-02-07)   
Maxthon4.0.3.6000700116000000000000016/11573ES5.1 (2013-02-07)   
Firefox19.07002193000000000000193/11573ES5.1 (2013-02-07)Nightly 21.0a1 (2013-02-09)7002209000000000000209/11573ES5.1 (2013-02-07)

ECMAScript, 4th Edition

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.[14] 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

Features under discussion for a future edition (originally "ECMAScript 4"; now ECMAScript Harmony) include:

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.

Bug fixes and backwards compatibility

In addition to introducing new features, some ES3 bugs were proposed to be fixed in edition 4.[15][16] These fixes and others, and support for JSON encoding/decoding, have been folded into the ECMAScript, 5th Edition specification.[17]

History

Work started on Edition 4 after the ES-CP (Compact Profile) specification was completed, and continued for approximately 18 months where slow progress was made balancing the theory of Netscape's JavaScript 2 specification with the implementation experience of Microsoft's JScript .NET. After some time, the focus shifted to the ECMAScript for XML (E4X) standard. 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,"[18] and that stakeholders who opposed the changes were being "hidden from view".[19] 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.[20] 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.[21]

ECMAScript, 5th Edition

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.[22][23] 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.[24] On December 3, 2009, ECMA-262 5th edition was published.[25]

ECMAScript Harmony (6th Edition)

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 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).[26] As of December 2009[update], there is no publicly announced release date for next edition within the ECMAScript Harmony trajectory. Depending on ECMA, that next edition may end up being called ECMAScript, 6th edition.

See also

References

  1. ^ RFC 4329
  2. ^ InfoWorld: JavaScript creator ponders past, future
  3. ^ JavaScript Press Release
  4. ^ Brendan's Roadmap Updates: Popularity
  5. ^ JavaScript Standardization Press Release
  6. ^ es4-discuss: Will there be a suggested file suffix for es4?
  7. ^ Zakas, Nicholas C. (2011). Professional JavaScript for Web Developers. John Wiley & Sons. ISBN 9781118233092. http://books.google.com/books?id=C3ka bcBG0ZsC&pg=PT770&dq=ecma-262 +harmony&hl=en&sa=X&ei=5p LlUJbFJsfQqAHC3IHQBw&ved=0CDEQ6AE wAA.
  8. ^ Changes to JavaScript, Part 1: EcmaScript 5
  9. ^ "About". ECMAScript. http://www.ecmascript.org/about.php. Retrieved 2009-12-17.
  10. ^ TypeScriptLang.org
  11. ^ "JavaScript - JScript - ECMAScript version history". Webmasterworld.com. http://www.webmasterworld.com/forum91 /68.htm. Retrieved 2009-12-17.
  12. ^ "Version Information (JScript)". Msdn.microsoft.com. http://msdn.microsoft.com/library/def ault.asp?url=/library/en-us/script56/ html/js56jsoriversioninformation.asp. Retrieved 2009-12-17.
  13. ^ "Introducing JScript .NET". Microsoft.com. http://msdn.microsoft.com/en-us/libra ry/ms974588.aspx#scripting0714_topic4. Retrieved 2010-01-12.
  14. ^ es4-discuss: ES4 overview paper released
  15. ^ John Resig - Bug Fixes in JavaScript 2
  16. ^ Incompatibilities between ES3 and ES4
  17. ^ [2][dead link]
  18. ^ IEBlog: ECMAScript 3 and Beyond
  19. ^ Albatross!: What I think about ES4
  20. ^ Brendan's Roadmap Updates: Open letter to Chris Wilson
  21. ^ Brendan's Roadmap Updates: My @media Ajax Keynote
  22. ^ ECMAScript Harmony announcement
  23. ^ Announcement of the 5th edition candidate by the specification editors
  24. ^ "Ecma International finalises major revision of ECMAScript". Ecma International. 2009-04-09. http://www.ecma-international.org/new s/PressReleases/PR_Ecma_finalises_maj or_revision_of_ECMAScript.htm. Retrieved 2009-05-22.
  25. ^ Ecma News: 98th General Assembly approved documents
  26. ^ John Resig: ECMAScript Harmony

External links

ISO Standard
Ecma Standards


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