Q:

Can a DOM object be an index/key in Javascript array?

Would like to maintain a map/hash of DOM objects. Can they serve as key objects? If not, what are the alternatives, please? If there are better ways - kindly enlist them as well.

A:

You can put anything as the key, but before actual use it is always converted to string, and that string is used as a key.
So, if you look at what domObject.toString() produces, you see it is not a good candidate. If all of your dom objects have an id, you could use that id.
If not, and you still desperately need a key based on DOM object, you probably could do with using, for example, _counter attribute with automatic counter in background putting new unique value in a DOM object if _counter is not yet present.

