+💯 > On Mar 20, 2017, at 11:15 PM, /#!/JoePea <[email protected]> wrote: > > Hey all, > > I'd like to have something like a WeakMap where the keys can be primitives > and the values are weakly-held Objects, so if there are no more references to > any of the Object values that the entry gets removed from the map. > > For example, it might look like this: > > ``` > { > ["foo"] => SomeObject, > ["​bar​"] => ​OtherObject​, > } > ``` > > where if there are no more references to `OtherObject`, then `['bar'] => > OtherObject` is removed from the map. > > Usage would be very similar to WeakMap, like > > ``` > let m = new ReversedWeakMap > > m.add('foo', SomeObject) > m.add('​bar​', ​OtherObject​) > ​console.log(m.get('bar')) // OtherObject > > ... time passes, no more references to OtherObject, OtherObject is collected > ... > > console.log(m.get('bar'))​ // undefined > ``` > > I thought of using WeakMap values as keys, and vice versa, but it seems to be > impossible. > > I guess maybe it is difficult to add this natively because it would mean that > GC needs to be completely deterministic as far as JS programs go. For example: > > ```js > let m = new ReversedWeakMap > > function main() { > m.set('foo', {}) > console.log(m.get('foo')) // {} > }() > > main() > > // GC would have to be guaranteed to have happened at this point. > > console.log(m.get('foo')) // undefined > > ``` > > > /#!/JoePea > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss
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