You're mixing up what you need to do and what is a good language. Use javascript if that's the "best" language you know. Have I said otherwise, I think not.
It also seems your got some beef with your collegue C/C++ developer, take that up with him!
I have seen webassembly from C++, who knows if that was the best solution, maybe it actually was at that particular moment.
And if you can solve all your problems in javascript, you do so, good for you. I just think it's a bit ridiculous when people boast that "their" programming language is the "best" one. That "best language" changes all the time, you'll see by yourself.