JavaScript has been my goto language for the last two years, I love writing it, and at this point would consider it to be my strong suit. When learning JavaScript initially I was already familiar with Java so the process was pretty smooth. I read all six of the You Don't know JS books by Kyle Simpson, and Secrets of the Javascript Ninja (link) to get my feet wet with scopes & closures, memoization, the event loop and es6 syntax. After about a year of practice I jumped down the functional programming rabbit hole and that's when I really started to see how powerful and flexible Javascript could be. Things like currying, partial application, and even observables with RxJS are all things that I have become comfortable with and love using to make my code as modular and easy to reason about as possible. I am comfortable writing async code whether it be with promises, callbacks, async await, generators, or observables. The context of most of my JavaScript development is within React at the moment, but I also am comfortable using it server-side with NodeJS.