Closure in JavaScript

A closure is a fundamental concept in JavaScript that allows functions to retain access to variables from their outer scope even after the outer function has finished executing. It is an important concept for understanding JavaScript's scoping and is widely used to create private variables and functions, as well as in event handlers and asynchronous programming.

Closures play a crucial role in creating and working with functions that have persistent state and encapsulation. In this article, we'll explore what closures are, how they work, and some practical examples of their usage.

To understand closures, let's understand the basics:

Lexical Scope:

In JavaScript, the scope of a variable is determined by its location within the source code. This concept is known as lexical scoping. Each function creates its own scope, and nested functions have access to variables in their outer (parent) scopes.

Function Scope:

Variables defined within a function are only accessible within that function's scope and any nested functions. When a function is executed, a new scope is created, and variables declared within that function become local variables.