Pure JavaScript – Christian Johansen will show you how you can significantly up your game by leaving loops behind and embracing functions … We'll learn about JavaScript promises as well, and I'll talk about how we can learn from functional programming when developing in JavaScript. The bad news is arrays are functors, so you can't escape them. Functional programming patterns for the non-mathematician – Learn about practical use cases for functors, applicatives, and monads. M: [T] -> [T] where T is a given type. Monads If you do Giving a definition of monad is somewhat tedious and requires a bit of theory, so we are first going to build an intuition for them through examples. We start off by creating a constructor that stores a value: const MayBe = function(val) { this.value = val; } MayBe.of = function(val) { return new MayBe(val); } The good news is arrays are monads, so when you get into this situation of … But monads do. Totally valid, you could do that. According to me, Promises are Functors, Applicative Functors and Monads since they obey the functor and monads laws. Let's first try with map: You wouldn’t claim to ‘understand’ monads, but you can see how using Maybe might save a lot of effort. MayBe Functors. [1,2,3]--> [1,1,2,2,3,3]). This is part 3 in a series on Functional Programming in javascript. By Daniel Weiner, Software Engineer, Breakthrough Technologies In this article I'll talk about a concept that is prevalent in functional programming: monads. I know, those words can be frightening. But functors do not place any such restriction. Array Monad. Functors and monads can provide additional utility and types when working with JavaScript. “Monads” apply a function that returns a wrapped value. A discussion on functors can easily get very formal and theoretical. Monads wrap types giving them additional behavior like the automatic propagation of empty value (Maybe monad) or simplifying asynchronous code (Continuation monad). The type signature of an array monad is. Functional Programming In JavaScript — With Practical Examples (Part 1) Functional Programming(FP) can change the way you program for the better. The reason for this is that, like all functional programming techniques, functors originate from mathematics—in this case, category theory. That is why map is a functor but not a monad. I write javascript I'm just going to ignore these functor things and I won't need monads". Ok, lets study the functor case. There are many other methods that they may contain, but these core methods are the required basis for their classification. To be considered a monad the structure has to provide three components: type constructor — a feature that creates a monadic type for the underlying type. A Map to Success: Functors in Javascript by Kevin Welcher (a functor is just an object that implements map(), so monads are functors that implement a couple of extra things on top). For Promises to be an instance of Functor we must define an fmap function (a -> b) - f a -> f b for Promises and fmap shall pass the Functor laws. Part 1: The Unit; Part 2: The Monoid; Part 4: The art of chaining different monads; After discovering the Unit and the Monoid, it's time to talk about Functors and Monads. Their definitions are frightening, too: Functor In the end they are containers which serve a specific purpose and follow a series of rules. In this article, we’ll look at how to pipe functions and functors with JavaScript. functors: you apply a function to a wrapped value using fmap or <$> applicatives: you apply a wrapped function to a wrapped value using <*> monads: you apply a function that returns a wrapped value, to a wrapped value using >>= Graphic Let's write a function that duplicates every item in an array (e.g. A MayBe functor is one that lets us implement a map function in a different way. Slowly, it begins to make sense. 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