I don't see how it would be possible in ES6 user code to ever make a Map/Set or a Map/Set subclass instance immutable, since `Map.prototype.set.call`/`Set.prototype.add.call` will operate on any Map/Set-like object's `[[MapData]]`/`[[SetData]]` internal slot. The only thing I can think of would be using a Proxy to a collection rather than a collection itself.
I'm probably missing something - can anybody confirm or refute? On Thu, Apr 30, 2015 at 1:25 PM, Boris Zbarsky <[email protected]> wrote: > On 4/30/15 3:46 PM, C. Scott Ananian wrote: > >> I like the idea of snapshot methods, but they can be implemented in user >> code using subclasses in ES6. >> > > Can they? You can't create immutable snapshots in user code afaict... > > But that would still have required an explicit test in >> Map.clear/set/delete to ensure that they were operating on an instanceof >> Map and not just on a ReadOnlyMap. >> > > More likely an internal slot check, not an instanceof check. > > -Boris > > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss >
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