Clojurescript has been the real hero for me coming from a heavy Javascript background. The UI patterns are basically 1:1 with the functional standards in Javascript land, but you're working with a language that has immutable data structures by default (I can ditch Immutable.js) and the core library has all those goody functional helpers I'd include ramda or lodash for.
But in addition to that, shadow-cljs is truly incredible, kudos to Thomas Heller. When developing, my editor is connected to the browser app through a repl, and I can switch namespaces and sort of TDD new code, or debug an issue by cracking into the actual pipeline and interactively spelunking. In JS land, everything is transpiled, so really you have to put debuggers, refresh the page or action, catch the debugger, and do stuff that way. If you're developing new code you can't test out a function if it uses some transpiled feature, so you write a test or do the debugger thing.
It's takes some dedication to get there, and you don't need emacs even though it's really fun to learn and get proficient in. I use Spacemacs and am constantly learning some new package that's installed to help me. I recently switched from parinfer to paredit, and it's reaalllllly cool. With the repl driven development and structural editing you can achieve this kinda mind-meld with your development process. I don't think that necessarily makes this better than Javascript, but if you're into stuff like that there's a really high skill-cap with how you can optimize your development workflow.
And really, at it's core to me Clojurescript is like my perfect Javascript. There were not any new concepts for me to learn as I had been programming Javascript functionally for some time, it's just everything I wanted in Javascript without the friction and bolt-on libraries.
For developer happiness, it has a ton to offer, and there's always something else to dig in to.