Discere faciendo (learn by doing).
This answer is a cliche, but it is a cliche for a reason -- it really is the best way to learn and lucky for you it is highly applicable to development where access to computers is cheap and access to all the information you could ever want is even cheaper.
Instead of defining your goals in terms of "I need to learn X, Y and Z about JavaScript and HTML", define your goals in terms of "I want to build this website which I'm pretty sure might require X, Y and Z in JavaScript", all of which I will have to learn as part of the process.
I don't mean this to be a dig at you personally, but as a 40 year old who had to learn mostly out of whatever paper books and manuals I could scrounge up from local libraries, I'm kind of flabbergasted by questions like this appearing because... well, I've got to assume you have access to the Internet. Which has, like, everything on it. Everything! Perhaps in a way we swung too far too fast and the issue now is information overload, but 15 year old me would have killed for access to the type of information that is now just a google away.