Is there a way to read a set of JavaScript files, and output a description of where every function/method is defined?

I realize that this is likely impossible in full generality, due to the extreme dynamic nature of the language. What I'm imagining is something which gets the (relatively) straightforward cases. Ideally, I'd want it figure out where, e.g. some method got attached to string or hash or some other fundamental class (and also just let you find all the classes/functions that get defined once in one place).

Does such a tool exist?