What is closure?

A closure means a function remembers the scope in which it was created.

function createCounter() {
  let count = 0;

  return function () {
    count++;
    return count;
  };
}

const counter = createCounter();

counter(); // 1
counter(); // 2
counter(); // 3

Even though createCounter() has already finished, the inner function still has access to count.

Uses:

• private state,
• callbacks,
• factory functions,
• event handlers,
• memoization.