konami.js

var keys = [];
document.onkeyup = function(e) {
  keys.unshift(e.keyCode);
  keys = keys.slice(0, 10);
  if (keys.join(';') === [65, 66, 39, 37, 39, 37, 40, 38, 40, 38].join(';')) {
    alert('konami!');
  }
}