JavaScript cross browser addLoadEventListener() #onload #load

addLoadEventListener

function addLoadEventListener (listener) {
  var done, oldonload;

  if(typeof addEventListener !== "undefined") {
    return addEventListener("load", listener, false);
  }

  if(typeof attachEvent !== "undefined") {
    return attachEvent("onload", listener);
  }

  oldonload = onload;

  if (typeof onload !== 'function') {
    onload = listener;
  }
  else {
    onload = function () {
      oldonload && oldonload();
      listener();
    }
  }
}