[afiori]

Not arguing for or againts something, this is just something I wanted to say.

Framing matters here, the API of Promises in js maps almost nicely to the common monad API of bind (then), join (implicitely done by the runtime whenever possible), and return (Promise.resolve). Learning any monads is unlikely to be harder than this as these operations are indeed quite intuitive.

What is often referenced with learning monads is instead Learning All the Monads, sometimes adding a touch of Learning All the Monad Transformers and interactions of different monads. This intrinsecally needs to be done in a generic/parametric way and is way harder.

To my knowledge Haskell is the most mainstream[1] language only typed language that allows expressing the categorical definition, most other type systems are significantly more limited in how much maths/category theory they can express and often focus on specialized functionality with practical implication like Rust's ownership system or Typescript's Capitalize<StringType> that only exists to allow nicer typing of some common API desings[2]

[1] most mainstream typed language at least, you can implement Monad is JS/TS but the language cannot express it the same way C cannor express generics even if you can manually implement them in it.

[2] https://www.typescriptlang.org/docs/handbook/utility-types.h...

[kaba0]

Otherwise agree with you, just noting that Scala is likely even more mainstream than Haskell and has proper Monads.