Agreed. CoffeeScript is a leaky abstraction of JS; the underlying paradigm of JS still peeks out even though it's papered over (see the fat arrow =>).

Once you have a grasp of JS (and the things you might not like about it), you can then move to CS. When something looks a bit off in CS, you'll probably be able to translate why it is that way due to the JS underpinning.

Intentionally "leaky" ;) Martin Fowler has written a good post about how and why this is desirable:

http://martinfowler.com/bliki/TransparentCompilation.html