Scope of Event Listeners

function addListener(element, event, listener, bubble) {
  if(element.addEventListener) {
    if(typeof(bubble) == "undefined") bubble = false;
    element.addEventListener(event, listener, bubble);
  } else if(this.attachEvent) {
    element.attachEvent("on" + event, listener);
  } else {
    debug("Could not set up event listener");
  }
}

function getSource(event) {
  if(event.target) { return event.target; }
  else if(event.srcElement) { return event.srcElement; }
  debug("Could not find event source: " + event);
  return undefined;
}

var body = document.getElementsByTagName("body").item(0);
var div = document.createElement("div");
body.appendChild(div);
var scopeTest = function(event) {
  var scope = "unknown";
  if(this == window) { scope = "window"; }
  else if(this == arguments.callee) { scope = "callee"; }
  else {
    scope += " (" + this + ")";
    if(this.nodeName) { scope += " {" + this.nodeName + "}" };
  }
  var message = "Scope of callback to: ";
  var source = getSource(event);
  message += "{" + (source ? source.nodeName : "No Source") + "}";
  debug(message + ": " + scope + " [" + this.userData + "]");
}

var fileImage = new Image();
fileImage.userData = "file image user data";
addListener(fileImage, "load", scopeTest);
fileImage.src = "../tree_view/file.png";
div.appendChild(document.createElement("a"));
div.lastChild.userData = "a #1 user data";
addListener(div.lastChild, "click", scopeTest);
div.lastChild.appendChild(fileImage);

function wrapper(event) {
  var source = getSource(event);
  if(source) { arguments.callee.handler.apply(source, arguments) }
  else { arguments.callee.handler.apply(this, arguments) }
}
wrapper.handler = scopeTest;

var folderImage = new Image();
folderImage.userData = "folder image user data";
addListener(folderImage, "load", wrapper);
folderImage.src = "../tree_view/folder.png";
div.appendChild(document.createElement("a"));
div.lastChild.userData = "a #2 user data";
addListener(div.lastChild, "click", wrapper);
div.lastChild.appendChild(folderImage);