[ghusbands]

A WeakMap works with objects as keys. You can do it with objects you don't control, without adding some sort of id field. It can't be fully simulated with a WeakRef.

One common use is to associate extra data with objects, without attaching it to those objects directly. In your map, you add an obj->extradata mapping. Having the target be a WeakRef would just mean you'd lose your extradata while the source obj is still around.