I learned JS by building GWT and Dart applications, then telling the compiler not to minify the JS, then reading through the JS to see if I understand what's going on. That's probably a lot harder than it needs to be.
Tony Alicea has some excellent JS tutorials, try this YouTube video, if you like it, get the full 12 hour course which will teach you how to write your own JS Libraries: youtube.com/watch
In the full course, you will enhance your abilities as a Javascript developer by delving into first class functions, callbacks, closures, IIFEs, prototypal inheritance, diving into the source code of jQuery, and building your own small framework/library.