What are your use cases for it? Rather than tying it to being a `Map`, I'd prefer to see something like Java's [`WeakReference`][1]: You could store the `WeakReference`s in a `Map` if you wanted strongly-referenced keys with weakly-referenced values.
-- T.J. Crowder [1]: http://docs.oracle.com/javase/8/docs/api/java/lang/ref/WeakReference.html On Tue, Mar 21, 2017 at 6:15 AM, /#!/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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