Listens for the Konami code, runs a callback when detected.

konami.js

/**
 * Konami
 *
 * Listens for the [Konami code][1], runs a callback when detected.
 *
 * [1]: https://en.wikipedia.org/wiki/Konami_Code
 *
 * Example usage:
 *
 *     import { konami } from './konami.js/';
 * 
 *     konami(() => {
 *       console.log('Hello, Konami!');
 *     });
 *
 */

export function konami(fn, {
  pattern = [38, 38, 40, 40, 37, 39, 37, 39, 66, 65],
} = {}) {
  const keys = [];
  window.addEventListener('keydown', ({ keyCode }) => {
    keys.push(keyCode);
    if (keys.length > pattern.length) keys.splice(0, 1);
    if (keys.join(',') === pattern.join(',')) fn();
  });
}