Would be interested to hear more about this game. How long does this take during work time, the evaluation criteria you hit on (is this testing your IDE setup, your knowledge of build tools, features of the tech stack like threading, etc etc)
This might handle scripts as you described, but just wait until it needs the context of random bits of a tens-of-millions-of-lines monorepo plus knowledge of custom infrastructure that isn't documented anywhere and--oh wait, we can't actually let this LLM-as-a-service read our code because X and Y compliance/security/legal/etc, even if we ran it on-prem.
The robots aren't coming for you so soon, don't worry.
After this and saying that you're a beginner to JS, I would instead suggest spending time to develop perspective from a place of knowledge and experience rather than... I guess, being proudly ignorant?
Mypy is just okay. Haven't used TS to know the dark corners there, but any type system that's bolted on to the language is going to have dark corners in the best case.
It's better than no type system, however. I remember when typed languages were "bad" because it "slowed you down" and "wasn't necessary if you know what you're doing"... how naive I was when I repeated those words so many years ago :)
As a previously front-end gone full-stack gone and settled in backend/infra... don't bother. But if you have to bother, or really, really want to 🙂, pick a relatively popular thing (e.g. Vue), and learn that, ignore the rest. By the time you come up for air the new hotness will have changed anyways, and the wheel will have been reinvented twice. It's a moving target, just learn the fundamentals with something and you'll be good to go.