And come on, JS is a C-style language. If you know one you know them all.
It's also not a difficult jump to OOP languages; especially now that Java 8 supported lambdas and C# supports async/await. It's hard to learn concepts, not syntax.
At least that's the case if it's logically similar. C, Java, JS, etc are mostly transferable. I might not say the same about something like Haskell.