I was considering picking up react but I don't know very much about html and css right now. However that is something I want to learn as well. It would be nice to get some library recommendations from people who know more about this than I do.
Too long for a comment, but not really an answer, because there is not really a question :-/
It depends on your requirements (if you edit your question to give those, it will be un-held and we will answer). Welcome aboard, bit please read [ask]. We don’t do “best” questions – one man’s best is another man’s worst; see Is it acceptable to use 'best' in a question? et al.
If you want two way data binding, use Angular(Js) (unfortunately , Google switched AngularJs language from JS to TypeScript & no longer develop the JS version, but millions still use it).
Vue is great & lightweight, similar to Angular in its use of directives, but only has one way data binding out of the box (although you can add 2 way on).
ReactJs is very popular, and might be a good choice if you might later want to use React Native to develop cross-platform Android & iOs apps. They are two separate languages/frameworks, but with a great deal of overlap.
Ember is also extremely popular, but how can I know if it meets your requirements when you don’t have any, other than “best”?
And, of course, JQuery is the one that started it all & still has extremely wide support & following.
In short, please read [ask] and update your question to tell us which features you want, or just google – there are plenty of “best JS” sites out there.
Finally, you say :
I don't know very much about html and css right now
forget about JS. You need a firm understanding of those first.
VanillaJS was voted the best JS library/frame work last year -
I agree - if I have to code in JS, I'd rather use Vanilla than anything else. But then, I'm a "boxes full of parts to full functional back end" guy.