How to Create and Use JavaScript Functions

Functions are a fundamental building block of JavaScript, allowing you to encapsulate and reuse code. In this guide, we'll explore how to create and use JavaScript functions, providing examples to illustrate each concept.

Creating Functions

You can create functions using the function keyword, followed by a name and a pair of parentheses. You can also define parameters inside the parentheses:

// Function with no parameters
function greet() {
console.log("Hello, world!");
// Function with parameters
function add(a, b) {
return a + b;

Calling Functions

To execute a function, you call it by its name, followed by parentheses. If the function has parameters, you pass arguments inside the parentheses:

greet(); // Calling the greet function
const result = add(5, 3); // Calling the add function with arguments

Returning Values

Functions can return values using the return statement. You can then store or use the returned value:

function multiply(a, b) {
return a * b;
const product = multiply(4, 7);
console.log("Product:", product);

Function Expressions

Functions can also be defined as expressions and assigned to variables. These are often referred to as anonymous functions:

const subtract = function(a, b) {
return a - b;
const result = subtract(10, 4);
console.log("Result:", result);

Arrow Functions

Arrow functions provide a concise way to define functions. They are often used for short, one-liner functions:

const square = (x) => x * x;
const area = (length, width) => length * width;

Function Scope

Functions create their own scope. Variables declared inside a function are not accessible outside of it:

function printName() {
let name = "John";
console.log(name); // This will result in an error


JavaScript functions are versatile tools for organizing and reusing code. They play a vital role in JavaScript development and enable you to build complex applications by breaking code into manageable pieces.

Happy coding!