Version shipped in Firefox 3.5. Released on June 30, 2009. Includes the TraceMonkey JIT and supports native JSON.
Version shipped in Firefox 3. Released in June 2008. Includes expression closures, generator expressions and Array.reduce()
Version shipped in Firefox 2. Released in October 2006. Includes generators, iterators, array comprehensions, let expressions, and destructuring assignment.
Version shipped in Firefox 1.5. Released in November 2005. Includes ECMAScript for XML (E4X), new Array methods plus String and Array generics.
Version shipped in Netscape Navigator 6.0 and Firefox 1.0. Release on November 14, 2000. Standardization work to be compliant with ECMA-262 3rd Edition.