do not work shortcutkey

gistfile1.js

var keyElement = aWindow.document.createElement("key");

keyElement.setAttribute("key", key);
keyElement.setAttribute("modifiers", modifiers);
keyElement.setAttribute("oncommand", "void(0);");

keyElement.addEventListener("command", function() {
  alert('do command');
}, false);

aWindow.document.getElementById("mainKeyset").appendChild(keyElement);