^ I spend a lot of time in both Javascript and C++, I think your original observation is good, on a base level- the two languages, even though they "look" a bit similar, are very different in a whole bunch of ways and take a bit of a different way of thinking to use each one very effectively. Same as whatever other language. I find even C++ vs C# takes a bit of a different mindset.
I've been doing some reading lately about about languages that support design-by-contract features - and I think stuff like that highlights why it might be good to learn more languages. Each one sort of has it's own patterns built into it, their own way of thinking, their own way of accomplishing similar stuff. Some of those patterns could possibly carry over into another language, or provide a hint as to how you might want to approach something regardless of what language you're in.
