I'm definetly not the most experienced around here, but from my limited knowledge I would highly recommend you learn JavaScript. It will allow you to build much more functional websites and most modern sites make use of JQuery and many times Bootstrap to make them professional and mobile-friendly (both of which utilize JavaScript). Ontop of that, if you ever decide to go into the profession the merit of knowing JavaScript will definetly weigh in your favour as most front-end developers (as far as I know) are practically required to know it nowadays. As I mentioned earlier though, I'm not really in a position to give you a definite answer, you might want to wait for someone more experienced to give their input.
EDIT: Oh, Neko already replied.