Kas sa saad selgitada, mis on sulgemine JavaScriptis ja kuidas see töötab?

Closure in JavaScript is a function that «remembers» the environment in which it was created, even if that environment is no longer active. Simply put, a function inside another function can access the variables of the outer function after the outer function has finished executing.

This works because when a function is created, a reference to the lexical environment where it was declared is preserved.

Example:

function outer() {
  let counter = 0;
  return function inner() {
    counter++;
    console.log(counter);
  };
}

const counter = outer();
counter(); // 1
counter(); // 2

Here, inner closes over the variable counter from outer, maintaining its state between calls.