I don't know why I've never knew that freeCodeCamp has such thorough curriculums. That's so great!
Lots of people have mentioned MDN, its good.
Hackerrank is one I used when I was teaching myself Python. Its great because it teaches you by giving you a conceptual snippet and then a problem to solve with an integrated code editor. The downside is the problems are written and created by the community so sometimes the quality is bad. Oh and they have regular competitions and offer services to connect you with companies looking to hire coders.
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