Discover

'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', after the two primary implementations of the specification.

Contents

History

Versions

Dialects

!

Version correspondence

Fourth edition

See also

References

External links

History

JavaScript was originally developed by Brendan Eich of Netscape under the name Mocha, later LiveScript, and finally renamed to JavaScript. In December 1995 Sun Microsystems and Netscape announced JavaScript in a press release^[2]. In March 1996 Netscape Navigator 2.0 was out, featuring support for JavaScript.
Due to the de facto success of JavaScript as a client-side scripting language for web pages, Microsoft developed a compatible language known as JScript including new date functions that fixed JavaScript's Y2K non-compliant functions, which was included in Internet Explorer 3.0, released in August 1996.
Microsoft submitted the JScript 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.
The name "ECMAScript" was a compromise between the organizations involved in standardizing the language, especially Netscape and Microsoft. Brendan Eich, the creator of JavaScript, is on record as saying that "ECMAScript was always an unwanted trade name that sounds like a skin disease."^[3]

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, editor Guy L. Steele, Jr.
2	June 1998	Editorial changes to keep the specification fully aligned with ISO/IEC 16262 international standard; editor 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; editor Mike Cowlishaw.
4	Work in progress	Multiple new concepts and language features - see the section "Fourth edition" 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 is one place where the ECMAScript Compact Profile is used in favour of full ECMAScript in order to reduce processing and memory requirements on a device.

Dialects

ECMAScript is supported in many applications, especially web browsers, where it's commonly called JavaScript. Dialects typically include their own, different standard libraries, of which some are standardized separately – such as the W3C-specified DOM. Some implementations, such as ActionScript used in Flash, have a completely different set of libraries. This means that applications written in one dialect of ECMAScript will not likely work in another, unless they are designed to be compatible.

Application	Dialect	Latest dialect version	Corresponding ECMAScript edition
Mozilla Firefox7, the Gecko layout engine, SpiderMonkey, and Rhino	JavaScript	1.7	ECMA-262, edition 3 1
Internet Explorer	JScript	5.7	ECMA-262, edition 3
Opera	ECMAScript, with extensions to both JavaScript and JScript	1.3/1.5	ECMA-262, edition 3
KHTML layout engine, KDE's Konqueror, and Apple's Safari8	JavaScript	1.56	ECMA-262
Microsoft .NET Framework	JScript .NET	8.0	ECMA-262, edition 3 2
Adobe Flash and Adobe Flex	ActionScript	23	ECMA-262, edition 3 3ECMA-262, edition 4 4
Adobe Acrobat	JavaScript	1.5	ECMA-262, edition 3
General purpose scripting language	DMDScript	1.06	ECMA-262
OpenLaszlo Platform	JavaScript	1.4	ECMA-262, edition 3 5
iCab	InScript	3.22	ECMA-262, edition 3
Max/MSP	JavaScript	1.5	ECMA-262, edition 3
Samba 4 and embedded servers. (ASCII only, no floats; removes: ''try catch throw break continue switch while do with = ! <<< >>>'', prefix ++ --, regular expressions, array and object literals, ''Number, Date, Regex'', various methods)	Embedded JavaScript		ECMA-262

Note (1): Gecko 1.8.1 has partial support of E4X [1] and a few other features, see New in JavaScript 1.7.
Note (2): 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.
Note (3): In addition to supporting ECMA-262 edition 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): Adobe asserts it implements the preliminary edition 4 of ECMA-262 [2]
Note (5): As stated by OpenLaszlo, it partially implements edition 3 of ECMA-262 [3]
Note (6): The current Webkit binaries, as of April 2007, also implement at least part of the Javascript 1.6 extras
Note (7): The Mozilla implementations, (SpiderMonkey in the C programming language and Rhino in the Java programming language), are used in several third-party programs, including the Yahoo! Widget Engine (Konfabulator) and the Macintosh system-level scripting language JavaScript OSA.
Note (8): Apple's Safari uses JavaScriptCore which is based on the KDE KJS library.

Version correspondence

The following table is based on [4] and [5]; 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: E4X, Array extras (e.g. Array.prototype.forEach), Array and String generics [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]) [7]
	JScript .NET (ASP.NET; no IE release)	(JScript .NET is said to be designed with the participation of other ECMA members)
JavaScript 2.0		Edition 4 (Work in progress; see the section "Fourth edition" below). JavaScript 2.0 will not be backwards compatible with versions 1.6 and 1.7. JavaScript 2.0 uses the JavaScript 1.5 specification as the base of its specification, therefore it will not support E4X. Refer to ECMA-262 Fourth Edition.

Fourth edition

The ECMA-262 fourth edition is the first major update to ECMAScript since the third edition published in 1999. The new version of the language is backwards compatible with ECMAScript 3 while adding multiple new features, such as:

★ Classes

★ Packages and namespaces

★ Optional static typing

★ Generators and iterators

★ Destructuring assignment (likely)

★ JSON Encoding/Decoding
An export of ECMAScript 4 committee wiki is located at
http://developer.mozilla.org/es4/ (note that the wiki is not exported regularly, so those documents are likely to be outdated).
ECMAScript 4 intends 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.

See also

★ List of ECMAScript engines

★ Document Object Model

★ JavaScript

★ ActionScript

★ Tamarin (JIT)

References

1. RFC 4329
2. http://wp.netscape.com/newsref/pr/newsrelease67.html
3. https://mail.mozilla.org/private/es4-discuss/2006-October/000133.html

External links

★ ECMAScript 4 Reference Implementation

★ Standard ECMA-262 ECMAScript Language Specification 3rd edition (December 1999)

★ Standard ECMA-290 ECMAScript Components Specification (June 1999)

★ Standard ECMA-327 ECMAScript 3rd Edition Compact Profile (June 2001)

★ Standard ECMA-357 ECMAScript for XML (E4X) Specification (June 2004)

★ Export Root of the ECMAScript 4 Committee Wiki