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JavaScript was created at Netscape in the early days of the Web, and technically, "JavaScript" is a trademark licensed from Sun Microsystems(now Oracle) used to describe Netscape‘s(now Mozilla‘s) implementation of the language. Netscape submitted the language for standardization to ECMA-the European Computer Manufacturer‘s Association- and because of trademark issues, the standardized version of the language was stuck with the awkward name "ECMAScript". For the same trademark reasons, Microsoft‘s version of the language is formally known as "JScript". In practice, just about everyone calls the languages JavaScript. This book uses the name "ECMAScript" only to refer to the language standard.
For the last decade, all web browsers have implemented version 3 of the ECMAScript standard and there has really benn no need to think about version numbers: the language standard was stable and browser implementations of the language were, for the most part,interoperable. Recently, an important new version of the language has been defined as ECMAScript version 5 and, at the time of this writing, browsers are beginning to implement it. This book covers all the new features of ECMAScript 5 as well as all the long-standing features of ECMAScript 3. You‘ll sometimes see these language versions abbreviated as ES3 and ES5, just as you‘ll sometimes see the name JavaScript abbreviated as JS.
When we‘re speaking of the language itself, the only version numbers that are relevant are ECMAScript versions 3 or 5.(Version 4 of ECMAScript was under development for years, but proved to be too ambitious and was never released.) Sometimes, however, you‘ll also see a JavaScript version number, such as JavaScript1.5 or JavaScript1.8. These are Mozilla‘s version numbers: version 1.5 is basically ECMAScript 3, and later versions include nonstandard language extensions.(see Chapter 11). Finally, there are also version numbers attached to particular JavaScript interpreters or "engines." Google calls its JavaScript interpreter V8, for example, and at the time of this writing the current version of the V8 engine is 3.0.
JavaScript: Names and Versions
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原文地址：http://www.cnblogs.com/specification/p/4545114.html
