It’s not elegant, but there is a way to do type checking in CoffeeScript: http://coffeescript.org/#type-annotations

This is cool! That being said, it would be very nice to have (optional) syntactically more beautiful type annotation. I assume Flow must be compatible with regular javascript, but CoffeeScript could take more flexible approach. I have no idea what the actual syntax could be, though.

Thanks for the link. :)

But wow, "not elegant" is an understatement.

> If CoffeeScript added an (optional) type system I'd switch back in an instant.

The home page talks a little about achieving this by using Flow annotations in Coffeescript source and then having the build system pass the Javascript output to Flow: http://coffeescript.org/#type-annotations

That would be really nice, but CoffeeScript will probably not be adding types unless they start adding them to JavaScript.

It is a dilemma, but so far I have gotten by without type-checking.

Well, guess it's time for someone to build yet another layer of abstraction by writing a typed superset that compiles-to-CoffeeScript then!

(I'm joking, but actually.. why not?)

call it ToffeeScript - a dialect of CoffeeScript that transpiles to TypeScript?

I'm afraid you're a few years too late!

https://github.com/jiangmiao/toffee-script

You might like LightScript: http://lightscript.org

Good interop with Flow isn't quite there yet, though.