Javascript Clouser

A closure is a function that has access to variables in its outer (enclosing) scope, even after the outer function has returned. Closures are a powerful feature of JavaScript that allows you to create functions with persistent state and private variables. In this answer, we’ll explore closures in depth with an example.

Example 1: Counter Function

Let’s start with a simple example of a closure that creates a counter function. This function will return a new number each time it is called, starting at 1 and increasing by 1 each time.

function createCounter() {
  let count = 0;
  
  return function() {
    count++;
    return count;
  }
}

const counter = createCounter();

console.log(counter()); // 1
console.log(counter()); // 2
console.log(counter()); // 3

In this example, createCounter is a function that returns another function. The inner function has access to the count variable in the outer scope of createCounter. Each time the inner function is called, it increments the count variable and returns its new value.

When we call createCounter, it returns a new instance of the inner function, which we assign to the counter variable. We can then call counter multiple times to get the next number in the sequence.

Example 2: Private Variables