Concepts of Functional Programming in Javascript

After a long time learning and working with object-oriented programming, I took a step back to think about system complexity.

“Complexity is anything that makes software hard to understand or to modify.” — John Outerhout

Doing some research, I found functional programming concepts like immutability and pure function. Those concepts are big advantages to build side-effect-free functions, so it is easier to maintain systems — with some other benefits. In this post, I will tell you more about functional programming, and some important concepts, with a lot of code examples. In Javascript! What is functional programming? Functional programming is a programming paradigm — a style of building the structure and elements of computer programs — that treats computation as the evaluation of mathematical functions and avoids changing-state and mutable data — Wikipedia. Pure functions benefits The code’s definitely easier to test. We don’t need to mock anything. So we can unit test pure functions with different contexts: Given a parameter A → expect the function to return value B Given a parameter C → expect the function to return value D A simple example would be a function to receive a collection of numbers and expect it to increment each element of this collection.