JavaScript Functions - Function Expressions

Function expressions are a way to define and use functions in JavaScript. Unlike function declarations, function expressions allow you to create functions on the fly and assign them to variables. In this guide, we'll explore JavaScript function expressions and provide examples to illustrate their usage.

Defining a Function Expression

A function expression is created by assigning an anonymous function to a variable:

const greet = function(name) {
return `Hello, ${name}!`;

In this example, we've defined a function expression called greet that takes a name parameter and returns a greeting string.

Using Function Expressions

You can use function expressions just like any other function:

const result = greet("Alice");
console.log(result); // Outputs: "Hello, Alice!"

The greet function expression is called with the argument "Alice," and the result is printed to the console.

Anonymous Function Expressions

Function expressions can also be anonymous, which means they have no name:

const add = function(x, y) {
return x + y;

Anonymous function expressions are often used when a function is used once or as an argument to another function.

IIFE - Immediately Invoked Function Expressions

An Immediately Invoked Function Expression (IIFE) is a function expression that is invoked immediately after its creation:

(function() {
console.log("I am an IIFE!");

IIFE is useful for creating isolated scopes and avoiding global variable pollution.


Function expressions are a flexible and powerful way to work with functions in JavaScript. They allow you to define functions on the fly, create anonymous functions, and use IIFE for encapsulation. Understanding function expressions is essential for writing clean and modular JavaScript code.

Happy coding!