As already mentioned in the thread, it depends on what you want your students to learn. My universities CS courses (aside from theoretical stuff) started with Racket for the basic concepts, good choice. We were then taught Java to handle a small project, questionable. But after that we had no problems with the language, when we had to implement algorithms, which would look quite similar in most other OO languages, maybe with added memory management.
I think JavaScript's prototype-based inheritance and global scope would make it hard to abstract concepts learned in it to other languages. Strict ES6 might help a bit. When switching from Scheme + Java to JS, you can get the Java+Scheme mix, that JavaScript is in my eyes, and use it accordingly. Switching the other way round you would basically have to relearn the concepts, because JavaScript does not express one distinct enough, but is an exotic mix of them (or an ugly hack as others might say).
Outside of CS though, I think introducing people to JavaScript, PHP or even advanced Excel is highly beneficial.
I think JavaScript's prototype-based inheritance and global scope would make it hard to abstract concepts learned in it to other languages. Strict ES6 might help a bit. When switching from Scheme + Java to JS, you can get the Java+Scheme mix, that JavaScript is in my eyes, and use it accordingly. Switching the other way round you would basically have to relearn the concepts, because JavaScript does not express one distinct enough, but is an exotic mix of them (or an ugly hack as others might say).
Outside of CS though, I think introducing people to JavaScript, PHP or even advanced Excel is highly beneficial.