[CyberFonic]

I find that learning "pure JS" is the key. The various frameworks are great for productivity but it is easy overlook the principles and learn the framework specific way of doing things. ES6 introduces features that were missing in earlier versions and needed polyfills, external tools and frameworks.

The two resources that I found to be most useful are:

http://eloquentjavascript.net

and

http://exploringjs.com/es6/

[jimmahoney]

I second "Eloquent Javascript" - it's excellent.