ECMAScript

ECMAScript is a scripting programming language, standardized by Ecma International in the ECMA-262 specification. The language is widely used on the web, and is often referred to as JavaScript or JScript, although those two languages are extensions of the ECMA-262 standard.

Please see the JavaScript article for an overview of the language.

History

In December 1995 Sun Microsystems and Netscape Communications Corporation introduced ^* JavaScript. In March 1996 Netscape Communications Corporation released Netscape Navigator 2.0, which featured support for JavaScript. Due to the de facto success of JavaScript as a client-side scripting language for web pages, Microsoft developed a "roughly" compatible language known as JScript, which was included in Internet Explorer 3.0, released in August 1996.

Netscape submitted the JavaScript specification to Ecma International for standardization; the work on the specification, ECMA-262, began in November 1996. The first edition of ECMA-262 was adopted by the ECMA General Assembly of June 1997.

ECMAScript is the name of the scripting language standardized in ECMA-262. Both JavaScript and JScript technologies aim to be compatible with ECMAScript, while providing additional features not described in the ECMA specification.

Versions

There are three editions of ECMA-262 published, and the work on the fourth edition is in progress.

Edition	Date published	Differences to the previous edition
1	June 1997	First edition
2	June 1998	Editorial changes to keep the specification fully aligned with ISO/IEC 16262 international standard.
3	December 1999	Powerful regular expressions, better string handling, new control statements, try/catch exception handling, tighter definition of errors, formatting for numeric output and other.
4	Work in progress	Maybe explicit class definitions, packages and namespaces, optional static typing, better exposure of previously internal features (properties, key enumerability), and more?

In June 2004 Ecma International published ECMA-357 standard, defining an extension to ECMAScript, known as E4X (ECMAScript for XML).

Dialects

ECMAScript is supported in many applications, especially web browsers. The binding with DOM is added for manipulating the document.

Application	Dialect	Latest dialect version	Corresponding ECMAScript revision
Gecko-based browsers and other applications embedding SpiderMonkey	JavaScript	1.6	ECMA-262, revision 3 ¹
Internet Explorer	JScript	5.6	ECMA-262, revision 3
Opera	ECMAScript, with extensions to both JavaScript and JScript	1.3/1.5	ECMA-262, revision 3
KHTML based browsers	JavaScript	1.5	ECMA-262
Microsoft .NET Framework	JScript .NET	8.0	ECMA-262, revision 3 ²
Adobe Flash	ActionScript	2/3	ECMA-262, revision 3 ³
Adobe Acrobat	JavaScript	1.5	ECMA-262, revision 3
Any valid ECMA use	DMDScript	1.06	ECMA-262
OpenLaszlo Platform	JavaScript	1.4	ECMA-262, revision 3 ⁴
iCab	InScript	3.22	ECMA-262, revision 3

Note (1): The latest versions of SeaMonkey 1.8 and Firefox 1.5 have partial support of E4X and a few other features, see [http://developer.mozilla.org/en/docs/New_in_JavaScript_1.6 New in JavaScript 1.6.

Note (2): Microsoft claims that JScript 8.0 supports "almost all of the features of the ECMAScript Edition 3 Language Specification" but does not list the unsupported features.

Note (3): In addition to supporting ECMA-262 revision 3, ActionScript 2 also included support of properties, methods, and mechanisms that were proposed in early draft specifications of as yet unseen versions of ECMAScript. It remains to be seen if ActionScript will stay in sync with future changes to the ECMAScript specifications.

Note (4): As stated by OpenLaszlo, it partially implements revision 3 of ECMA-262 ^*

The Mozilla implementations, (SpiderMonkey in the C programming language and Rhino in the Java programming language), are used in several third-party programs, including Konfabulator and the Macintosh system-level scripting language JavaScript OSA.

Apple's Safari uses JavaScriptCore which is based on the KDE KJS library.

Version correspondence

The following table is based on and [http://msdn.microsoft.com/library/default.asp?url=/library/en-us/script56/html/js56jsoriversioninformation.asp; items on the same line are approximately the same language.

JavaScript	JScript	ECMAScript
1.0 (Netscape 2.0, Mar 1996)	1.0 (IE 3.0 - early versions, Aug 1996)
1.1 (Netscape 3.0, Aug 1996)	2.0 (IE 3.0 - later versions, Jan 1997)
1.2 (Netscape 4.0, Jun 1997)
1.3 (Netscape 4.5, Oct 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, Mar 1999)
	5.1 (IE 5.01)
1.5 (Netscape 6.0, Nov 2000; also later Netscape and Mozilla releases)	5.5 (IE 5.5, Jul 2000)	edition 3 (Dec 1999)
	5.6 (IE 6.0, Oct 2001)
1.6 (Gecko 1.8, Firefox 1.5, November 2005)		edition 3, with some compliant enhancements
1.7 (Gecko 1.8.1, Firefox 2.0, Fall 2006), an extension of JavaScript 1.6 still under development
	JScript .NET (ASP.NET; no IE release)	(JScript .NET is said to be designed with the participation of other ECMA members)
JavaScript 2.0 (proposal)		edition 4 (work in progress)

Fourth edition

The current work on the fourth edition of ECMAScript has received some criticism, as there is thought to be a concerted effort by the organization to change the language from a prototype-based programming language into a more traditional class-based programming one, in essence, changing the very nature of how JavaScript treats relationships between objects. JavaScript is often championed by prototype-based language advocates, as it is the best known language with this object-oriented feature. ActionScript version 2.0 is an example of a ECMAScript implementation which is already more class-based than prototype-based.

External links