None of them. Depends on what kind of project you are doing. But it is great to know Javascript better first.

Does someone is going to ask this question every month?

Vanilla JS. Period.

Vanilla JavaScript.

The biggest problem of development (as a whole, not just front end development) is the existence of frameworks. Most developers, especially freshmen and juniors, donʼt know what they deal with. They think in terms of DOM, bidirectional bindings, and all the like, instead of understanding how the language or the running environment (in this case, browsers) work.

You canʼt effectively harness frameworks if you donʼt understand the fundamentals of your job.

ReactJS is not a Framework, it's a library ;)