JavaScript Functors Explained - DZone

In essence, a functor is nothing more than a data structure you can map functions over with the purpose of lifting values from a container, modifying them, and then putting them back into a container. Simply put, it is a design pattern that defines semantics for how fmap should work. Here’s the general definition of fmap: fmap :: (A -> B) -> Wrapper(A) -> Wrapper(B) The function fmap takes a funct