[AstralStorm]

JS interpreter, thanks to asm.js, can be used to run any language. Knock yourself out.

Of course you get to deal with a bit of FFI when calling built-in functionality of the browser.

[sametmax]

Thanks to adapters, you can plug an american fridge in a french socket. I'll still buy the one made for the local electrical system.

[AstralStorm]

So, you'd write in an inferior language when even web framework authors don't want to?

(See CoffeeScript, TypeScript, Elm, etc. Or Transcrypt if you want pythonic semantics.)

I understand this being a business requirement made by a business droid. Other than that, there is really no reason to be married to JavaScript.