ES6 module to handle the Konami code input in a browser.

konami-code.js

const _code = "38384040373937396665";

export default class CheatCode {

  code = '';
  delay = 1500;
  callbacks = [];
  timeout = null;

  constructor() {
    this.handler = this.handler.bind(this);
    this.dispatch = this.dispatch.bind(this);

    document.addEventListener("keydown", this.handler, false);
  }

  handler(e) {
    try {
      clearTimeout(this.timeout);
    } catch (error) { }

    this.code = String(this.code + e.keyCode);

    if (this.code === _code) {
      this.dispatch("cheat code");
    }

    this.timeout = setTimeout(() => {
      clearTimeout(this.timeout);
      this.code = '';
    }, this.delay);
  }

  listen(callback) {
    if (typeof callback === "function") {
      this.callbacks.push(callback);
    }

    return this;
  }

  dispatch() {
    for (let i = this.callbacks.length; i--;) {
      this.callbacks[i]();
    }
  }
}

Refactored to ES6 from https://github.com/ProperJS/KonamiCode