[jarrett]

I love Underscore (and Haskell), but I wouldn't consider Underscore an FRP framework at all. It's functional, yes, in the sense that it provides some of the most common FP operations like map, filter, etc, using lambdas. But I don't see the reactive part. Maybe there's some kind of reactive feature tucked away in Underscore's rather large feature set, but I haven't seen it, and it's certainly not core to the library.