Design patterns·Functional ideas that went mainstream
you had a value in a box, a function returning another box, and needed one box out rather than a box in a box.
Monad
Also calledmonadic, flatMap, bind
A type that wraps a value along with an operation for chaining functions that themselves return the wrapped type — flatMap, bind, then — obeying a couple of laws. Promises, optionals, results and streams are all instances, which is why chaining them all feels the same. The useful, honest version for an interview is that it is a shared interface for sequencing computations in a context, not a metaphor about burritos.