<konami-code>

Web Component (with Polymer) to listen the Konami Code (↑↑↓↓←→←→BA).

Example:

<konami-code></konami-code>
<p>Type the Konami Code to launch the easter egg.</p>

<script>
  var konamiCode = document.querySelector('konami-code');
  konamiCode.addEventListener('code-completed', function(event) {
    alert('Easter egg!');
  });
</script>

<!--
You also can use the Polymer annotated event listener setup:
<konami-code on-code-completed="_launchEasterEgg"></konami-code>
-->