On a small tangent, it turns out you can provide a nearly perfect shim for WeakMap given ES5. That is: O(1) lookup time, keys hold reference to values strongly and not vice versa, being a WeakMap key or value doesn't prevent an object from being gced, weakmaps themselves can be gced while object/keys in it still exist, key->value mappings are non-forgeable and non-interceptable, and all of this done [almost] non-observerably. This gist by Gozala demonstrates the concept in action ( https://gist.github.com/1269991). I built on the technique he used as well as some ideas from the SES WeakMap impl by Mark Miller ( http://code.google.com/p/es-lab/source/browse/trunk/src/ses/WeakMap.js ) and redid my original not-so-good es6 collection shim with one that is very close in functionality and interface to the real thing: https://github.com/Benvie/ES6-Harmony-Collections-Shim . Compatibility goes to IE9 (relies on defineProperty and getOwnPropertyNames).
On Thu, May 10, 2012 at 12:34 PM, Mikeal Rogers <[email protected]>wrote: > > People in the community don't ask for "WeakMap" until there is a proposal. > Instead they come up with other crazy ways to accomplish their end goals > without needing such a type to varying degrees success (we're still finding > leaks in FreeList in node.js http.js that might have been prevented had we > had WeakMap a few years ago). > >
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