So I decided to start learning some actually used modern languages now on the advice of several professional developers I know (moving away from C for the time being), and I decided to make a few programs in JS before I finish SmartNotes CE. Does anybody know of a good lightweight but powerful and capable 2d javascript game engine? I would be making a shoot-em-up sort of game somewhat like calcuzap but with more features and higher res graphics (obviously because it would be running on computers).

JS is good, although to pull a mateo on you, I'd definitely improve your skills at C. However the industry is changing and JS is being used more and more, also it's nice to take a break to work on something else some times.

Back to the actual question asked:
Here's a good list on js libraries from github.