Update 2012-01-23: “ECMAScript 6 support in Mozilla” on the Mozilla Development Network.
The next version of ECMAScript (code-named ECMAScript.next ) will be standardized by 2013. This post enumerates the first features that are currently being tested in Firefox and Chrome.
DEFINE_bool(harmony_typeof, false, "enable harmony semantics for typeof") DEFINE_bool(harmony_scoping, false, "enable harmony block scoping") DEFINE_bool(harmony_proxies, false, "enable harmony proxies") DEFINE_bool(harmony_collections, false, "enable harmony collections (sets, maps, and weak maps)")Andreas Rossberg elaborates:
... the --harmony flag currently activates the following experimental features for V8:
On the browser side, that should become functional in Chrome 17 (some of it is in 16 already, but incomplete/buggy) by setting
- block scoping, let, const, block functions
- [old] proxies, though not direct proxies yet
- maps and sets
- weak maps
- typeof null reform--js-flags="--harmony"If you are on the Chrome dev channel, you should also see it show up on chrome://flags soon.