JavaScript · Collections, storage and utilities

Closure

A function keeps access to variables from the scope where it was created, even after that scope returns.

javascriptRunnable example javascript course

Syntax

outer variable captured by inner function

Example

Try it

function counter() {
  let count = 0;
  return () => ++count;
}
const next = counter();
console.log(next(), next());

Reference pages are the quick answer. The course explains the why, shows the full example and ends with a challenge.