Near perfect except it can't have the required GC behavior. It is impossible to emulate the required GC behavior outside of the garbage collector. That's why WeakMap exists.
Allen On May 10, 2012, at 6:19 PM, Brandon Benvie wrote: > 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). > > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss
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