I'm definitely not a js engine expert but isn't there some pointer-of-pointer thingy that points rearranged position(maybe called handle)?
I leaved the exact comparing rule as black box and let engines care such cases. The single rule is that it should be deterministic. Anyway, your WeakMap-based implementation can easily exceeds Number.MAX_SAFE_INTEGER with some long-running application, as numbers cannot be reused. 2016. 9. 19. 오후 6:03에 "Michał Wadas" <[email protected]>님이 작성: > > On Mon, Sep 19, 2016 at 7:32 AM, Park Hyeonu <[email protected]> wrote: > >> I'm sure this feature is already implemented for every modern js engines, >> as it's needed to implement Map/Set. >> > > But you know that, it's indeterministic and implementation is free to > reorganize pointers? > > a = {}; b = {}; > Object.compare(a,b); // 1 > gc.enforceGC(); > Object.compare(a,b); // -1 > > So any userland structure can't rely on persistence of order. > > Moreover, such ordering can be implemented with WeakMap. > > const wm = new WeakMap() > let i = 0; > function getId(obj) { > if (!wm.has(obj)) > wm.set(obj, i++); > return wm.get(obj); > } >
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