The JavaScript language has evolved since its original release in Netscape 2.0. There have been several versions of JavaScript:
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JavaScript 1.0, the original version, is supported by Netscape 2.0 and Internet Explorer 3.0.
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JavaScript 1.1 is supported by Netscape 3.0 and mostly supported by Internet Explorer 4.0.
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JavaScript 1.2 is supported by Netscape 4.0 and partially supported by Internet Explorer 4.0.
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JavaScript 1.3 is supported by Netscape 4.5 and Internet Explorer 5.0 and 6.0.
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JavaScript 1.5 is partially supported by Internet Explorer 6.0, and supported by Netscape 6.0 and Firefox 1.0.
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JavaScript 1.6 is currently supported by Firefox 1.5.
Each of these versions is an improvement over the previous version and includes a number of new features. With rare exception, browsers that support the new version will also support scripts written for earlier versions.
The European Computer Manufacturing Association (ECMA) has finalized the ECMA-262 specification for ECMAScript, a standardized version of JavaScript. JavaScript 1.3 follows the ECMA-262 standard, and JavaScript 1.5 follows ECMA-262 revision 3.