WeakSets and WeakMaps are awesome, but also have limitations.

This library exposes a WeakSet and WeakMap class that utilize weak references yet support iteration, including size, forEach(), entries(), keys(), values() etc.

Additionally, they allow you to mix objects and primitives and it just works.

IterableWeakSet is a subclass of Set that uses WeakRef objects under the hood to store the values. IterableWeakMap is a subclass of Map that uses WeakRef objects under the hood to store the keys. They intercept all relevant methods to unwrap the weakrefs when read from the outside and remove any values that have been garbage collected.

As a result, this means things like .size or iterator values may change between calls, as the garbage collector works its magic. That’s why the built-in objects are not designed this way!