I've been doing web development in some form or fashion since 1999 (as an aside, the Wayback Machine even has a snapshot of one of my old websites; what a world)! I probably started picking up JavaScript way back in the early 2000s, as my web developing knowledge improved. Since web browsers are generally really good at supporting the old way of doing things, my knowledge of JavaScript has been pretty stagnant for a long time.
Not too long ago, I stumbled upon The Modern JavaScript Tutorial, a terrific resource for learning how to do things the modern way. I'm working my way through reading it, even taking the time to go back over the basics. I've already learned a lot; some of what I've been doing has apparently been deprecated for a while now, which was interesting to learn.
I've also learned about features I hadn't seen before (the nullish coalescing operator being one of those). I recommend it if, like me, you're still living in the dark ages.