The big player in the filed is react. There are tons of components out there and a big ecosystem.
So before you start learning react, you need seemingly to learn how to use and configure webpack and babel and how to write ES2015. It may be great if you program 8h a day.But it is also new barrier, demotivating (learn x and y before you can do z!) and I might learn some statistics instead.
Anyhow, for now I started to learn vue.js Vue is far smaller than react. It's ecosystem is smaller, too. It demands less tools. Let's see how this journey continues. I sometimes miss jQuery.
Notes: * Related for Python: Virtualenv is an anti-pattern (for beginners). * Added 2019-12-05: HTML, CSS and our vanishing industry entry points. * Added 2019-12-05: I have been using vue since quite some time (3 years, it seems?!) for smaller things. Its ecosystem also often assumes to use a toolchain, but it is less baked into the whole project.