3 ms·

Do Promises and async-await work together better than, say, Promises and Lua-like stackful coroutines?

• z3t4 6y ago
  I dont know Lua, but async/await in JavaScript is syntax sugar for a coroutine.
• WorldMaker 6y ago
  This description is probably far more abstract than most would like (and it is probably wrong by not being exact enough, I am not a mathematician I am a software developer), but might be useful to some: coroutines are a join calculus and Promises are a monad. async/await is syntactic sugar for a monad (less general than Haskell's do-notation, more general than only Promises, though rarely in practice used much beyond Promises). You could plumb Promises on top of coroutines easily (and while JS engines are more traditionally event loops; other languages that support async/await such as Python use much more coroutine-like underbellies), and while you don't get the full "join calculus" power/flexibility by putting the monad abstraction on top of the join calculus, you get the benefit of monad transformers like async/await. Those benefits being that the async/await syntax and semantics for working with Promises more closely resembles the imperative code it replaces, whereas the join calculus is its own [sometimes easy, admittedly] learning curve with its own syntax and semantics. Most of the complaints about Promises are the usual complaints about monadic wrapping types that the types become "viral" and "color" all associated code. But that just means that the failure cases are more easily picked up by a static type checker than semantic failures in learning the join calculus.