If you take these courses (in this order), you can achieve a good understanding fast:
Andrew Mead’s Udemy Courses
Andrew’s Node course is also a good one.
Will Sentance’s Pluralsight Courses
The Hard Parts, The New Hard Parts, The Hard Parts of Object Oriented Programming are all great from Will. I was not that impressed with his Node course, and I have not taken the functional programming one yet.
Bogdan is from Ukraine if I am not mistaken and he has put together an awesome course. It will deepen the understanding of all the basics of the language, how OOP is working and more. It also has lots of exercises that are actually interesting. A word of warning, he has a thick accent. It was not a problem for me as I am a non-native English speaker as well. Some of you may have trouble with that but in my opinion it’s worth to work through the course. I cannot praise it enough.
While you are going through these courses, you will start using MDN and Stackoverflow. W3Schools is also good for a quick check, but if you want real deep documentation of certain features, you will end up on MDN.