[temporarysdwvit]

Oh you can, just implement toString and js will use it for hashing

[IshKebab]

No it won't.

[yqot]

Map, no. Plain object, yes.

[IshKebab]

It doesn't "use `toString` for hashing", it just converts the key to a string. That is not the same (e.g. you can't recover the original key).