[lucian1900]

Various incarnations of the Promise monad have existed for quite a while, even in JS. The oldest one I can think of is MochiKit's Deferred, inspired by Twisted's. That one worked (and still does) seamlessly with any callback code.

[abecedarius]

(Twisted was inspired by the work I just pointed to in my answer. Not to take away from yours -- I wasn't familiar with MochiKit.)

[lucian1900]

Of course, using monads for asynchronous tasks is an old trick and E has always been ahead of its time (like many other languages ...)