[sokoloff]

The reason to develop a skillset in a different programming language is not because JS is such a widely popular ecosystem (on both the labor demand and labor supply sides), but because having a reasonable level of comfort in multiple languages makes you better as a programmer overall and therefore more likely to compete successfully in interviews and on the job (and, IMO, it's a damn lot of fun as well).

Even if you only ever wanted to work in JS and an infallible oracle told you that you'd never be out of work longer than a week at a time, I think you should still become reasonably familiar with a few other languages.

[john-radio]

Comfort and familiarity with a variety of languages is always a nice to have for a professional developer, but if the hypothetical oracle said the opposite, that focusing on JS would indeed limit OP's professional options, then that would be a much more compelling reason to go learn some Golang or whatever than just intellectual curiosity.

[twelve40]

yeah "better programmer overall" seems rather vague. The OP seems to be asking specifically "is it even worth it to stay in JS anymore", not "how do i become a well-rounded individual".

I personally prefer to hedge my bets by doing both backend and frontend work. If you join a smaller place/startup, you may end up having to push both. Saying, "I can build anything and I can help across the entire stack where needed" and showing history to back that up i think is a positive. Yes, a github project in a different stack might come in handy at an interview.

[sokoloff]

I left a few assumptions out of my response that may help anchor my advice back to the question as originally asked:

There will, for the next decade and likely the next two decades, be several million jobs that are using the Javascript ecosystem. (out of ~30M programmers worldwide). If OP (or anyone else) is happy enough working in that ecosystem and concerned only about ongoing employability, finding a way to be in the top 10% of Javascript programmers is more than sufficient. (Being in the top 25% is probably more than sufficient.)

If you start from a base case of 10K hours of JS experience, are you better off with that or instead having 9K hours of JS, 250 of a lisp, 250 of Java/C#, 250 of golang/rust, and 250 of SQL? I think the latter candidate is far more likely to be able to succeed and thrive in the JS world than someone with the "extra" 1K hours of JS experience.

I think you choose JS or not based on whether you like working in JS, then if you choose it, you find a way to maximize your chances for success, which I think is "something different from JS and happens to be 'become a well-rounded individual'."

[nassimsoftware]

This is exactly what I'm asking about. You hit the nail on the head.