Choose the tools/libs/framework you already know and that you're already comfortable with. Then I suggest you read the documentation on the Activity Streams website : http://activitystrea.ms/

I think the class keyword is just syntaxic sugar AND also enforce the misconception of the behavior of the "this". For those 2 reasons I stay away from class in javascript.

I like Xiao Meng's answer : "A framework differs from a library in one very important way: library code is always called by code that you write, while a framework always calls code that you write."