Marijuana done did a 180 in the last 50 years in terms of public opinion from being cited in Reagan's "War on drugs" speech as a dangerous drug to it being legalized in Colorado and Washington in 2012, for those who know about this plant's previous reputation know it was largely considered a gateway drug (as in the first drug try before getting into more serious drugs) and JavaScript is just* about the same.
Learning JavaScript is not going to give you an understanding on the broader realm of programming languages and computer science, it's just gonna make you highly qualified in googling for errors and remembering popular library API's, at least this is the case for me personally. JavaScript has failed and I know I am not alone because npm packages still getting published and the wheel of faith continues along it's path.

Nevertheless I shall turn the other cheek and thank this language for making me understand how hard it is to actually build software and how exhilarating it can be when you finally crack it. Given that, I would like to emphasize the utter fuckery of prototypal inheritance, the this keyword, undefined, stupid syntax errors and all the Es's, no matter how cute (ES6) or who their daddy is (Typescript), when a programming language has this much to learn about and practice it detaches itself from it's true objective, being efficient and understandable, it's not novelty when it's too much for so little. It's just some other bullshit one needs to do to keep their job، well I might not actually know what I am talking about only 3 years in, but every time I look at Eslint warning I feel my stomach turning so I will just use ReScript or Elm, and fuck SEO or I'll even switch to PHP, who knows what I will do, just a noob JS developer trying to figure out what lies beyond the wall.
I encourage others to do the same because life is too short to spend any of it using and relying only on JavaScript or it's little succubus frameworks and tools.

But I still recommend it for back end.