Comment by alphonse23

Promises and monads are way different though. Promises are used for "simplifying" asynchronous coding in imperative languages, and monads are a general computational methodology towards writing syntactically imperative-looking code in purely functional languages, built on top of type-classes. Without understanding why Haskell is purely functional, you couldn't even understand the motivation behind monads. And sure, you can extend a javascript prototype (or any object) to do something monad like, but without all of Haskell's strictness, you'd miss the jest.