JS is an on-demand language and it runs everywhere on the Internet. You want to design the front-end of the website- use JS; you want to modify the back-end- again you can use JS. This language is running in browsers like chrome and many others since 1995.
Other than developing and maintaining the front-end and back-end of the websites, JS can be used in many other projects.
You can also start remote freelancing or can work in a full-time position with a good pay scale. It is always better to upskill your efficiency to get a better opportunity in your career.
You can go for some YouTube channels as well to learn JS from the beginning.