Master typescript and you will be rewarded greatly! It is a fantastic tool with a very high level of adoption already. It makes React significantly easier to write and refactor. You won’t ever go back to plain .js!

Deno is not relevant enough, I would wager 99.99% of the existing projects you might find yourself working on in the next few years will be using node somewhere in the stack. It shouldn’t be hard to pick up deno when it eventually does show up.