The ability to treat functions as values in JavaScript, allowing you to store, pass them around, and utilize them similar to any other data type, is known as a first-class function.

What Is First Class Function In Javascript

First class function in js with example
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JavaScript has established itself as a flexible language in the world of programming, enabling programmers to create dynamic and interactive web applications. First-class functions, which allow functions to be considered as values, is one of its significant characteristics. This article goes into JavaScript’s first-class functions concept, examining their significance and providing real-world usage examples.

Understanding First-Class Functions:

First-Class Functions: Functions are first-class citizens in JavaScript, which means that they can be assigned to variables, used as arguments by other functions, and even have values returned by them. This idea has its origins in functional programming, a paradigm for writing computer programs that place a strong emphasis on the use of immutable, pure functions.

First class function in js
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Assigning Functions to Variables:

Let’s start by taking a closer look at the process of assigning functions to variables. With the help of this feature, we may store functions as values and refer to them using the names of the allocated variables. Think about the following instance:

const greet = function(name) {
  console.log(`Hello, ${name}!`);

greet("Ben"); // Output: Hello, Ben!

The value of the variable greet is given the function greet in this passage of code. The variable name can now be used to call the function, just like any other value.

First-class functions have the benefit of being able to pass other functions as arguments, which is one of its main advantages. As a result, it is possible to create higher-order functions that accept one or more functions as inputs. Let’s use the following case to demonstrate:

function applyOperation(num1, num2, operation) {
  return operation(num1, num2);

function add(a, b) {
  return a + b;

function subtract(a, b) {
  return a - b;

console.log(applyOperation(5, 3, add));      // Output: 8
console.log(applyOperation(5, 3, subtract)); // Output: 2

The applyOperation method in the code above accepts two numbers and an operation function. We can use the same applyOperation method to conduct various computations by passing several operation functions, such as add and subtract. This exemplifies the adaptability and flexibility that first-class functions offer.

Returning Functions from Functions:
The capability of first-class functions to return functions as values is an intriguing feature. As a result, we can generate functions on the fly depending on various assumptions or calculations. This allows us to create functions dynamically based on certain conditions or calculations Here is an illustration of this idea:

function createMultiplier(multiplier) {
  return function(number) {
    return number * multiplier;

const double = createMultiplier(2);
console.log(double(5)); // Output: 10

const triple = createMultiplier(3);
console.log(triple(5)); // Output: 15


The createMultiplier function takes a multiplier as an argument and returns a new function that multiplies any number passed to it by the given multiplier. This allows us to generate customized multiplier functions by invoking createMultiplier with different values.

First-class functions are a powerful feature in JavaScript that allows us to treat functions as values. This means that we can assign them to variables, pass them as arguments to other functions, and even return them from other functions. First-class functions promote code flexibility and abstraction, which can lead to cleaner, more modular, and reusable code.

In this article, we explored the concept of first-class functions in JavaScript and provided practical examples of their usage. However, it is important to note that this is just the tip of the iceberg when it comes to functional programming.

Here are some additional details about first-class functions:

  • First-class functions are a key feature of functional programming, which is a programming paradigm that emphasizes the use of functions as first-class values.
  • In functional programming, functions are treated as objects, which means that they can be passed around, stored in variables, and returned from other functions.
  • First-class functions can be used to create more complex and powerful code, such as recursive functions, higher-order functions, and anonymous functions.
  • First-class functions can also be used to improve the readability and maintainability of code.

I hope this helps!

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