JavaScript Tutorial for Programmers - Versions of JavaScript

There are several versions of JavaScript supported by certain browsers and browser versions. Unfortunately, this can often lead to confusion and incompatibilities. Since Netscape originally introduced JavaScript, JavaScript 1.0 was the language specification supported in Netscape Navigator 2.0. Subsequently, Navigator 3.0 supported new enhancements which comprised JavaScript 1.1. At present, Navigator 4.0 supports JavaScript 1.2.

In parallel, Microsoft attempted to support JavaScript 1.0 in their Internet Explorer 3.0 browser. Known as "Jscript," Microsoft's initial JavaScript support was unreliable and buggy. A push to standardize the language resulted in an "official" version of JavaScript sanctioned by the ECMA. Internet Explorer 4.0 includes robust support for the ECMA standardized JavaScript, which, although it shares much in common with Netscape's JavaScript 1.2, is not exactly equivalent.

While programming for any single version of JavaScript is relatively simple, writing code which functions across disparate versions, most notably Navigator 4 and MSIE 4, is one of the major challenges and topics of discussion in JavaScript programming at this time.

JavaScript Tutorial for Programmers
JavaScript Tutorial for Programmers
JavaScript Tutorial for Programmers - Embedding JavaScript