You asked which frontend JS framework/library you should learn, but I wonder whether the frontend or the JS part is more important to you.
frontend JS framework/library
If it's the former, then honestly, Elm is far simpler to learn than any JS framework IMO, thanks to the compiler being so helpful and actively giving you a hand figuring out what you need where. Any JS library or framework will help you get something on the screen faster, but actually getting to where you want to be will likely take a lot longer. As for learning resources, you can't go wrong with: frontendmasters.com/courses/elm/
But if you want to look at something free first, before diving in (with your wallet), then I'd also recommend the "Elm For Beginnners" course, which is free on knowthen.com
Honestly, I love JS, but I don't think it's a good starting point for anyone looking to learn about front-end development. I think it'll cause you to pick up bad habits without realising it, as well as not giving you especially helpful error messages when things go wrong, which leads to confusion and frustration.
The JS is important to me a little because I want to be more well versed with it and it's different frameworks. That being said I hadn't thought about elm and I'll definitely look into it.
If JS itself is a priority for you, then I agree with the people who have advised that you look to gain a better grasp of JS as a language, rather than just diving into a framework. This is just a personal recommendation mind, you may not find that this works for you if you're motivated more by instant gratification. You'll know how you learn best here. :-)
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