Showing popup when user leave the window

Question

Here's the code. I need to show pop up window, when user leave the window without using jquery. Anybody can help?

  <script type="text/javascript">
      function addEvent(obj, evt, fn) {
          if (obj.addEventListener) {
              obj.addEventListener(evt, fn, false);
          }
          else if (obj.attachEvent) {
              obj.attachEvent("on" + evt, fn);
          }
      }
      addEvent(window,"load",function(e) {
          addEvent(document, "mouseout", function(e) {
              e = e ? e : window.event;
              var from = e.relatedTarget || e.toElement;
              if (!from || from.nodeName == "HTML") {
                  // stop your drag event here
                  console.log("leave window");
              }
          });
      });
      </script>