[mijoharas]

One thing I haven't seen people suggesting here yet is to use a repl!

Import the thing, and then look at what it provides. If something seems useful, try calling the function/instantiating the class, if it gives you an error message, try with different arguments.

Hopefully, you should have some idea of what the library is trying to do, so you should be able to see some functions that look like they accomplish the kinds of things you want. Guess what kinds of arguments they take and try it. If you can't figure that out, jump into the source and figure it out.

I find it's much nicer working interactively like this than just reading the source because you can immediately try things out rather than jumping back and forth all the time.

Also, some languages like python have a `help()` function that you can call with any class/method/function to get to the docs on it (I can't remember anything like that for javascript, so you might be out of luck there).