Closures in Javascript and its applications

Closures are a fundamental concept in JavaScript, and they are used extensively in modern programming. Simply put, a closure is a function that has access to variables in its outer function scope, even after the outer function has returned. In this way, closures allow for data encapsulation and private variables in JavaScript.

One common use case for closures is to create private variables and methods within an object. For example, suppose you wanted to create an object that has a public method for incrementing a counter, but you don’t want the counter variable to be accessible from outside the object. Here’s an example of how you could use a closure to achieve this:

function counter() {
  let count = 0;

  return {
    increment: function() {
      count++;
      console.log(count);
    }
  };
}

const myCounter = counter();
myCounter.increment(); // logs 1
myCounter.increment(); // logs 2

In this example, the counter function creates a private variable count and returns an object with a public method increment. The increment method has access to the count variable due to the closure created by the counter function. When we call counter(), we get back an object with a single method, increment. We can then call myCounter.increment() to increment the count and log the current value.