Closure

In computer programming, a closure is a technique for implementing lexically {{glossary("scope", "scoped")}} name binding in a language with {{glossary("first-class function", "first-class functions")}}.

In {{glossary("JavaScript")}}, a {{glossary("function")}} creates a closure context. As shown by the following code, the inner function maintains access to the count variable even after createCounter() has finished executing.

function createCounter() {
  let count = 0;
  return function () {
    count += 1;
    return count;
  };
}

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

See also

• Closures in JavaScript
• Closure on Wikipedia