Was planning to :D looking it up now
56 karma · joined January 27, 2015
http://eloquentjavascript.net/1st_edition/chapter6.html
Also maybe look at larger libraries like underscore, lodash and get acquainted with the programming concepts they apply since they are well maintained libraries.
I read you are familiar with AngularJS, get into the source code, understand how the beast works. Get your hands dirty, maybe build something into the angular library itself just to test it out.
Look into stuff like functional programming, reactive programming, contextual programming. Learn the patterns and learn to apply them in your projects