In addition to all those other things that people mentioned, write a JavaScript interpreter.
You can't truly master a language until you know it inside and out. Implementing the language is a great way to do that. That's how I learned ML and Haskell. That's how I'm learning Lisp.
You can't truly master a language until you know it inside and out. Implementing the language is a great way to do that. That's how I learned ML and Haskell. That's how I'm learning Lisp.