Explain the concepts of functional programming in JavaScript Last Updated : 12 Feb, 2022 Summarize Comments Improve Suggest changes Share Like Article Like Report Every program we write follows an approach or style of writing also referred to as a paradigm. Functional programming is a declarative programming paradigm (programming paradigm where we write code in such a way that it describes the result and not the approach). To understand functional programming let's take an example of usual mathematics functions: y = f(x) this function does not modify the input passed in. Hence it is a pure function y'=g(f(x)) here we have two functions 'g' and 'f', we take the result of the function 'f' and use it in the function 'g', this concept is called functional composition. It encourages code reusability and maintainability. Similarly, in a functional code, the output depends only on the arguments that are passed to the function. Example: JavaScript const a = [6, 1, 9]; function push(a, element) { return [...a, element]; } console.log("Original array: ", a); console.log("Updated array: ", push(a, 10)); Output: Original array: [6,1,9] Updated array: [6,1,9,10] Here, we have created a function to push elements in an array, the push function is a pure function as it does not change the global array and only gives the result based on the input arguments. Core principles of functional programming: Immutable data: an immutable variable is one that cannot be modified after initialization or we can say that a variable can be assigned a value only once. The benefits of avoiding data mutation are that it makes the code easier to read and easier to test and debug.Pure functions: as discussed above, a function that always returns the same value for the same arguments is called a pure function. A good example for dealing with impurity in functions would be Redux, it handles all of the side effects affecting the main store and the logic composed of pure functions. Benefits of pure functions are:easy to testeasy to debugleads to smaller single-responsibility functionsDeclarative Style ( using functional composition ): it focuses on the result and not on the approach of the function. Composed functions make the code much more scalable as we have a clear separation of concerns Comment More infoAdvertise with us Next Article How to write a function in JavaScript ? S swapnil074 Follow Improve Article Tags : JavaScript JavaScript-Questions Similar Reads Functional Programming in JavaScript Functional Programming(FP) is as old as programming but some of us think that it is discovered recently because we found some parts in mathematics but not in the programming world. But nowadays functional programming is in trend. Almost every programming language including Java, Python, JavaScript, 4 min read Functional programming in JavaScript Functions are the most important part of functional programming (especially in JavaScript). Functions are the single source that helps developers to perform functional programming. Generally abbreviated as FP which revolves around functions and it is how we use functions that makes our code function 7 min read Explain the Different Function States in JavaScript In JavaScript, we can create functions in many different ways according to the need for the specific operation. For example, sometimes we need asynchronous functions or synchronous functions. Â In this article, we will discuss the difference between the function Person( ) { }, let person = Person ( ) 3 min read How to write a function in JavaScript ? JavaScript functions serve as reusable blocks of code that can be called from anywhere within your application. They eliminate the need to repeat the same code, promoting code reusability and modularity. By breaking down a large program into smaller, manageable functions, programmers can enhance cod 4 min read Introduction to Object Oriented Programming in JavaScript As JavaScript is widely used in Web Development, in this article we will explore some of the Object Oriented mechanisms supported by JavaScript to get the most out of it. Some of the common interview questions in JavaScript on OOPS include: How is Object-Oriented Programming implemented in JavaScrip 7 min read All about Functions and Scopes in JavaScript In this article, we will cover all the basic concepts of JS functions, callbacks, scopes, closures in-depth which would help you to - understand different types of function declarations.make better use of functions.understand how different scopes and scope chain works in JS.learn about closures and 10 min read Like