Closures in JavaScript

A closure allows an inner function to remember and access variables from its outer function, even after the outer function has finished execution.

What is a Closure?

A closure is created when an inner function remembers the variables of its outer function.

The inner function can continue to access those variables even after the outer function has completed its execution.

Example 1: Basic Closure

In this example, the inner function can access the variable declared inside the outer function.

function outerFunction() {

    let message = "Welcome to CIIT";

    function innerFunction() {
        console.log(message);
    }

    innerFunction();
}

outerFunction();

Example 2: Returning an Inner Function

A function can return another function. The returned function can still remember variables from the outer function.

function createMessage() {

    let message = "Hello JavaScript";

    return function() {
        console.log(message);
    };
}

let showMessage = createMessage();

showMessage();

Example 3: Counter Using Closure

Closures can be used to create private variables. Here, the counter variable is maintained by the returned function.

function createCounter() {

    let count = 0;

    return function() {

        count++;

        console.log(count);
    };
}

let counter = createCounter();

counter();
counter();
counter();

Important Points