How closure works in JavaScript ?

In this article, we will discuss about the closures working JavaScript. Let us first understand what exactly closures are and basic details which are associated with closures in JavaScript.

A Closure is a combination of a function enclosed with references to its surrounding state (the lexical environment). In JavaScript, closures are created every time a function is created at run time. In other words, a closure is just a fancy name for a function that remembers the external things used inside it.

Let us look at some examples to understand how closures actually work in JavaScript.

Example 1:

• In this example, we will be declaring a closure which would eventually access an outer variable balance from the outer function.
• After using the outer variable in inner most function, that particular closure will help us to deduct 100 from it, each time whenever that outer function is called.

Output:

Explanation: In the above example, currentbalance() can access outer variable balance hence balance is deducted by 100 each time initaccount() method is called. 

Example 2: Closures can be nested as well as in below example. Here in the example both outerfunction() and innerfunction() has access to counter variable , hence on calling Counter() both outerfunction() and innerfunction() increments the value of counter. In this context, we can say that closures have access to all outer function scopes.

Output: