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For example, [].map was "implemented in JavaScript 1.6." Is that an ES5 method? How does the 1.6 correlate to an ECMAScript version?

Bergi
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ryanve
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    "JavaScript 1.6" does not have any significant meaning outside Gecko-based browsers. Look through the [version overview pages](https://developer.mozilla.org/Special:Tags?tag=JavaScript_version_overviews) to browse the "changes history". – Rob W Jul 12 '12 at 21:28
  • @RobW Thanks—I wasn't sure about that either (whether those versions were something that Mozilla came up with or whether they came from somewhere else). – ryanve Jul 12 '12 at 21:37

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There aren't really strict correspondences between the version numbers Mozilla uses and the ECMAScript standard's version numbers. There's a table on Wikipedia that might be what you're looking for -- you'll see that JavaScript 1.6 corresponds to ECMAScript 3 and then some additional extensions. [].map specifically was standardized in ECMAScript 5, but to my understanding, the feature was first introduced by Firefox before the ECMAScript 5 standard was even published. (Firefox 1.5 which included JavaScript 1.6 was released on November 29, 2005, and the standard appears to have been published in September 2009.)

Casey Chu
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  • There are actually lots of features that were first introduced in SpiderMonkey/Firefox in one of the post-1.5 JavaScript versions and later made their way into ECMAScript 5. There are also lots of features that stayed SpiderMonkey-only, some of these will likely be part of ECMAScript Harmony. – Wladimir Palant Jul 12 '12 at 21:52