There are a couple of continuation-based web frameworks for Ruby (Borges, Wee), but they're old and abandoned as far as I know.

I suspect it didn't catch on because (1) people are afraid of continuations, and (2) web apps are typically designed in at least a pseudo-REST-like style, so the paradigm of "asking" the user (like "await" in ES6) isn't needed very often.

But it's a cool thing to be able to do, especially for funnel-type flows, and other types of more complex session-based interactions.

I wonder if there are any JavaScript inversion of control things for client side code. I've been working for the past week on a signup funnel with React and Flux, and it's just a big explicit state machine... which kind of works, but is also kind of tedious.