Had half a year to waste because it was too late to switch school level (I'm not even going to bother trying to translate this into weird USA school terms :P), I already knew quite a bit of MIPS (PSP hacking) by then, and wanted to try something else.
Don't know why I chose JavaScript, just did. Started with w3schools (ikr), eventually just learned by doing, doing and more doing. Along the way of doing I of course read the occasional article, "guide", best practices, documentations etc. No books and courses though.