What is a Closure in JavaScript?

What You'll Learn

• What closures are
• How they work
• Common use cases

What is a Closure?

A closure is a function that has access to variables from its outer (enclosing) scope, even after the outer function has returned.

Closures are created every time a function is created.

Example

function outer() {
  let count = 0;

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

const counter = outer();
console.log(counter()); // 1
console.log(counter()); // 2
console.log(counter()); // 3

Use Cases

• Data privacy (private variables)
• Event handlers
• Callbacks
• Module patterns