From https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Closures?redirectlocale=en-US&redirectslug=JavaScript%2FGuide%2FClosures

closures.js

function makeAdder(x) {
  return function(y) {
    return x + y;
  };
}

var add5 = makeAdder(5);
var add10 = makeAdder(10);

print(add5(2));  // 7
print(add10(2)); // 12