JavaScript

For language learning, I've always 1) come up with a simple project plan that's not too beyond my ability. Build a simple core that could branch off in several directions to make it more and more useful. I started one 10 years ago I'm still enjoying building on... and never needed to use objects ... OR frameworks ... to do anything.

It's good to know the basic, vanilla stuff really well. Say you're getting into text arrays, knowing basics of splice, slice, split, pop/push, indexOf, sort are a lot more useful than, say, typedArray. MDN is useful for details, but is very completist. And if you run into something new that you know you need to remember, try to use it ASAP, and as often as you can.

Lately I noticed the Digital Ocean tutorial series - it's very good, very well-written. https://www.digitalocean.com/community/tutorial-series/how-to-code-in-javascript

For a reference book with the essencials in one place, a hard copy of "Javascript - The good parts' by Crockford. Lots of expert examples, indexed, pick it up anytime ... it'll never get old! (Then pick up the essentials added in ES6.)