Command of the shortcut key does not work

gistfile1.js

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

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

keyElement.addEventListener("command", function() {
  openIncSearch(aWindow);
}, false);

mainKeyset.appendChild(keyElement);