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ECMAScript is a scripting language, standardized by Ecma International in the ECMA-262 specification and ISO/IEC 16262. The language is widely used on the web, especially in the form of its three best-known dialects, JavaScript, ActionScript, and JScript.
[edit] HistoryJavaScript 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 out, 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 java.util.Date.[4] JScript was included in Internet Explorer 3.0, released in August 1996. Netscape submitted JavaScript to Ecma International for standardization; 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.[6] ECMAScript is the name of the scripting language standardized in ECMA-262. Both JavaScript and JScript 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, whose disputes dominated the early standards sessions. 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."[7] [edit] VersionsThere are three editions of ECMA-262 published. Work on an update to the third edition known provisionally as "ECMAScript, Fifth Edition", and on a future edition codenamed "Harmony", is in progress.
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. [edit] FeaturesFurther information: ECMAScript features The ECMAScript language includes structured, dynamic, functional, and prototype-based features. [edit] SyntaxFurther information: ECMAScript syntax [edit] DialectsECMAScript is supported in many applications, especially web browsers, where it is commonly called JavaScript. Dialects sometimes include extensions to the language, or to the standard library and related APIs such as the W3C-specified 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. 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.
[edit] Version correspondenceThe following table is based on [1] and [2]; items on the same line are approximately the same language.
[edit] Future developmentThe 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.[10] 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. [edit] FeaturesFeatures 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 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. [edit] Bug fixes and backwards compatibilityIn addition to introducing new features, some ES3 bugs were proposed to be fixed in edition 4.[11] [12]. These fixes and others, and support for JSON encoding/decoding, have now been folded into the ECMAScript, 5th Edition specification.[13] [edit] HistoryWork 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 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,"[14] and that stakeholders who opposed the changes were being "hidden from view".[15] 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.[16] 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.[17] [edit] ECMAScript, 5th EditionMicrosoft, 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.[18] The "final" draft of the 5th edition (still subject to change reflecting the outcome of compatibility testing) was published April 2009. At that time Ecma announced testing of interoperable implementations was expected to be completed by mid-July, [19] although in fact it is still in progress. The standards track is expected to be finished by the end of 2009. [edit] ECMAScript HarmonyIn 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)[20] As of August 2009, there is no publicly announced release date for ECMAScript Harmony. Depending on ECMA, Harmony may end up being called ECMAScript, 6th edition. [edit] See also
[edit] References
[edit] External links
Categories: C programming language family | Curly bracket programming languages | JavaScript dialect engines | JavaScript programming language family | Object-based programming languages | Prototype-based programming languages | Computer and telecommunication standards | Scripting languages | Ecma standards | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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