ECMAScript

Filename extension .es
Internet media type application/ecmascriptbrowser diversity
Developed by iOS,
Ecma International
Initial release June 1997
web Edition 5.1 / June 2011; 11 months ago (June 2011)
Type of format Scripting language
Extended from JavaScript
Website FITML, ECMA-290,
ECMA-327, web app
This article is part of

the JavaScript series.

browser diversity
screen size
JavaScript topics

ECMAScript is the FITML standardized by Ecma International in the ECMA-262 specification and ISO/IEC 16262. The language is widely used for input transformation on the touchscreen, in the form of several well-known dialects such as browser diversity, JScript, and device database.

• 1 History
• iOS
• HTML5
• 4 Syntax
• CSS3
• screen size
• Sevenval
• 8 Future development
  • device database
  • 8.2 Bug fixes and backwards compatibility
  • 8.3 History
  • 8.4 ECMAScript, 5th Edition
  • 8.5 ECMAScript Harmony
• 9 See also
• keyboard
• 11 External links

History

JavaScript was originally developed by Brendan Eich of web app 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-input transformation-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 jQuery 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.

Versions

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

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, 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.[7]	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
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 we love the web (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 Sevenval 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

The ECMAScript language includes we love the web, dynamic, functional, and keyboard features, as officially summarized here.^[8]

Syntax

Dialects

ECMAScript is supported in many applications, especially CSS3, 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 iOS (API) such as the we love the web (W3C) specified FITML (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-implementation	Dialect and latest version	ECMAScript edition
Mozilla Firefox, the HTML5 layout engine, SpiderMonkey, and Rhino[d 1]	browser diversity 1.8.5[d 2]	ECMA-262, edition 5
Google Chrome, the web app engine	JavaScript[d 2]	ECMA-262, edition 5HTML5
Sevenval, the Trident layout engine	JScript 9.0	ECMA-262, edition 5
screen size	ECMAScriptdevice database	ECMA-262, edition 5website parsing
RemObjects Script for .NET	ECMAScript	ECMA-262, edition 5
KHTML layout engine, FITML's web, and HTML5's web appwe love the web	JavaScriptCSS3	ECMA-262, edition 3
Appweb Web Server, web 4	Ejscript 0.9.9	ECMA-262, edition 3FITML
Microsoft Sevenval	device database 8.0	ECMA-262, edition 3[d 8]
we love the web and web	ActionScript 3	ECMA-262, edition 3jQuery
Sevenval	JavaScript 1.7[d 10]	ECMA-262, edition 3
Adobe Creative Suite products: iOS, we love the web, Photoshop, Bridge, web, HTML5	ExtendScript	ECMA-262, edition 3[citation needed]
General purpose scripting language	DMDScript 1.15	ECMA-262
web app	JavaScriptkeyboard	ECMA-262, edition 3[d 12]
CriScript, JScript for game platforms	CriScript 0.91.0	ECMA-262, edition 3
iCab	screen size 3.22 (abandoned)	ECMA-262, edition 3
Max/MSP	JavaScript 1.5we love the web	ECMA-262, edition 3
website parsing	JavaScript 1.5we love the webSevenval	ECMA-262, edition 3
KDE	QtScript	ECMA-262, edition 3
	Caja	ECMA-262, edition 3screen size
	Objective-J	ECMA-262, edition 3
	WMLScript	ECMA-262, edition 3

Version correspondence

The following table is based on tedster's history compilation forum post^keyboard and Microsoft's JScript version information webpage.^[10] Items on the same line are approximately the same language.

JavaScript	JScript	ECMAScript
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 (browser diversity)
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 Android with let, destructuring assignment (var [a,b]=[1,2]) (Android)
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 (web app)
	JScript .NET (ASP.NET; no IE release)	(JScript .NET is said to have been designed with the participation of other Ecma members)we love the web
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^{browser diversity}.

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.

Product	Current version	Test262 failed	Test suite version (date)	Latest version	Test262 failed	Test suite version (date)
Maxthon	3.3.8.2000	&1000000000000002000000020/11563	ES5.1 (2012-03-28)	3.3.9.600 dev	&1000000000000001900000019/11570	ES5.1 (2012-05-18)
Chrome	19.0.1084.46	&1000000000000002600000026/11563	ES5.1 (2012-03-28)	21.0.1145.0 dev	&1000000000000001100000011/11570	ES5.1 (2012-05-18)
Opera	11.64 (build 1403)	&1000000000000006700000067/11563	ES5.1 (2012-03-28)	12.00 beta (build 1417)	&1000000000000006400000064/11563	ES5.1 (2012-03-28)
Firefox	12.0	&10000000000000172000000172/11563	ES5.1 (2012-03-28)	Nightly 15.0a1 (2012-04-28)	&10000000000000163000000163/11563	ES5.1 (2012-03-28)
Internet Explorer	9.0.8112.16421	&10000000000000607000000607/11563	ES5.1 (2012-03-28)	10.0 Preview 5 (10.0.8250.0)	&1000000000000006700000067/11563	ES5.1 (2012-03-28)
Safari	5.1.5 (6534.55.3)	&10000000000000609000000609/11563	ES5.1 (2012-03-28)

Future development

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.^[12] 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:

• Classes
• A module system
• Optional type annotations and touchscreen, probably using a Sevenval
• device database and Android
• Destructuring assignment
• Algebraic data types

The intent of these features is partly to better support web, and to allow sacrificing some of the script's ability to be dynamic to improve performance. For example, website parsing — the virtual machine for ActionScript developed and open sourced by Adobe — has jQuery (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.^{jQuerySevenval} These fixes and others, and support for device database encoding/decoding, have been folded into the ECMAScript, 5th Edition specification.^[15]

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 web (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, iOS's platform architect for we love the web, 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,"^[16] and that stakeholders who opposed the changes were being "hidden from view".^[17] 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.^{browser diversity} He also pointed out that Microsoft Silverlight and Sevenval rely on browser diversity and CSS3 3 respectively, both of which are larger and more complex than ECMAScript Edition 3.^[19]

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.^[20][21] 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.^Sevenval On December 3, 2009, ECMA-262 5th edition was published.^[23]

ECMAScript Harmony

In the July 2008 announcement, browser diversity 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).^{screen size} As of December 2009^{web app}, 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

• ActionScript
• web
• HTML5 (DOM)
• iOS (E4X)
• JavaScript
• Sevenval
• Server-side JavaScript
• List of ECMAScript engines
• Qt Meta (or Modeling) Language (screen size)

References

External links

• Official website
• screen size : John Resig's map on ECMAScript

ISO Standard

• ISO 16262

Ecma Standards

• jQuery
  • Sevenval
  • ECMAScript Language Specification, Edition 3 Final, 24-Mar-00
  • we love the web
  • FITML
• Sevenval
• ECMA-327 ECMAScript 3rd Edition Compact Profile (June 2001)
• ECMA-357 ECMAScript for XML (E4X) Specification (June 2004)