If you just want to learn the core language then there are any number of books available, or even just reading the MDN Web Docs thoroughly. It's a bit pointless

If you just want to learn the core language then there are any number of books available, or even just reading the MDN Web Docs thoroughly. It's a bit pointless to only learn the language though since you will be starting from scratch on any 'real' project that you attempt to do. Don't get me wrong, it's a good starting point but your journey will only be begun once you reach a 'perfect and complete level' of understanding. You'll quickly be forced to ask yourself what you want to accomplish with the knowledge you've gained and from there you will have to set yourself another course of learning the relevant APIs, frameworks, libraries, and tooling associated with that field. The fastest way to learn a language is to use it constantly, so my actual recommendation would be to begin by building a series of small toy projects. Build the classic ToDo app in whatever form you prefer. Build a calculator, a text editor, pong, an HTTP server, a database, a data visualization tool, a physics simulation, a paint program, etc., etc. None of them should be overly complicated, at first at least, but they will force you to think about how you use the language and will quickly show up the large gaps in your knowledge about it as well as point you in the direction of the current 'state of the art'. "Not hearing is not as good as hearing, hearing is not as good as seeing, seeing is not as good as knowing, knowing is not as good as acting; true learning continues until it is put into action." --Xunzi or if you prefer "What I cannot create, I do not understand." --Richard Feynman