(shameless plug) The state machine approach is one I used in an old sweetjs library called cspjs[1] which implemented async tasks into JavaScript well before as

(shameless plug) The state machine approach is one I used in an old sweetjs library called cspjs[1] which implemented async tasks into JavaScript well before async/await. I still think there are some good ideas left there - especially async error handling and native "data flow variables". [1] https://github.com/srikumarks/cspjs https://github.com/srikumarks/cspjs