I enjoy JS a lot, and will frequently choose it over Ruby or Python. A functional style plays nicely with a lot of the problems I'm solving, it's nearing ubiquity, and there's lots of big names and smart people working on optimizing it even more.
In my day job, we write mostly Coffee - which is little more than a preprocessor to JS, IMHO. It's definitely nice to have, but I don't consider it an independent language unto itself. If you know JS well, it shouldn't take more than a day to get up to speed with CS.
It's disappointing to see the false "JavaScript is functional" claim thrown around time and time again.
Just because it has first-class functions it does not mean that JavaScript is a "functional" language.
JavaScript does not promote the use of pure functions, referential transparency, and the minimization of state.
JavaScript does not encourage the use of recursion.
JavaScript has an atrociously broken type system, rather than a robust and theoretically sound one.
JavaScript does not offer pattern matching and other functionality offered by modern functional languages.
In fact, it goes out of its way to promote a very imperative, non-functional style of software development, even when efforts are made to try to use it in a functional way.
In my day job, we write mostly Coffee - which is little more than a preprocessor to JS, IMHO. It's definitely nice to have, but I don't consider it an independent language unto itself. If you know JS well, it shouldn't take more than a day to get up to speed with CS.