mostly-adequate-guide

So, this is going to be an uphill battle for you. I suggest you actually learn Haskell first, and then you'll be able to apply its lessons to TypeScript. Its tricky because these are patterns that are familiar in Haskell but are not really taught in other settings. Additionally, to really learn these, you need to experiment with them. Use them. etc. That's pretty hard to do if the learning resources are mostly in haskell and you don't really understand it. Alternatively, this might help: https://github.com/MostlyAdequate/mostly-adequate-guide Also alternatively, what I would do is just go slowly through the fp-ts code. Look at it a piece at a time and slowly grow your understanding. This may also help https://www.amazon.com/Domain-Modeling-Made-Functional-Domai...

There are a good deal of resources explaining these concepts in non-Haskell languages. This one is quite good and in javascript: https://github.com/MostlyAdequate/mostly-adequate-guide As far as functors this could be rephrased more comprehensibly to those unfamiliar with Haskell as "What is a Functor, really? Functor is an interface here are some definitions:" (typescript) interface ArrayFunctor<A, B> { map: (f: ((a: A) -> B), arr: Array<A>) -> Array<B> } interface PromiseFunctor<A, B> { map: (f: ((a: A) -> B), arr: Promise<A>) -> Promise<B> } interface ObservableFunctor<A, B> { map: (f: ((a: A) -> B), arr: Observable<A>) -> Observable<B> } "definitions" is plural here because typescript doesn't support higher-kinded types or else it might look like this: interface Functor<F, A, B> { map: (f: ((a