Polyfill for symbols as WeakMap keys?

Question

Polyfill for symbols as WeakMap keys?

matthew-dean opened this issue a year ago · comments

Is there polyfill support for this yet? https://github.com/tc39/proposal-symbols-as-weakmap-keys

On Node v16 at least I get a runtime error:

TypeError: Invalid value used as weak map key

Denis Pushkarev · Answer 1 · Sat Jul 08 2023 03:20:14 GMT+0800 (China Standard Time)

Hi. It's a good issue, but I don't think that it can be polyfilled without memory leaks, so I don't think that it's acceptable.

Denis Pushkarev · Answer 2 · Sun Jul 09 2023 14:45:54 GMT+0800 (China Standard Time)

I think that makes sense to add a note to this section: https://github.com/zloirock/core-js#missing-polyfills

Matthew Dean · Answer 3 · Mon Jul 10 2023 03:01:38 GMT+0800 (China Standard Time)

IMO it makes some sense to me to use a Map as a polyfill when a WeakMap can’t use a symbol. Yes it won’t release memory, but it helps someone ship to older versions of Node and (current) Firefox while using symbols with WeakMaps.

Denis Pushkarev · Answer 4 · Tue Jul 11 2023 15:51:06 GMT+0800 (China Standard Time)

The key moment of weak maps is weak semantics - it's contained in the constructor name. If you don't need weak semantics - usual maps are preferable. It's better immediately throw an error on a likely leak than allow it.