title: XMLHttpRequest.upload.addEventListener("progress"... not working
body: <p>I try to populate an upload bar by calling <em>XMLHttpRequest.upload.addEventListener("progress", progressHandler, false);</em>. Apparently my function <em>progressHandler</em> is not called at all. I do not have a clue, why. </p>
  
  <p>Everything else works fine, e.g. the call of <em>completeHandler</em>, after the file is completely uploaded. The upload of my testfile takes approx. 15 secs, so I would expect <em>progressHandler</em> to be called.</p>
  
  <p>Maybe someone can help me?</p>
  
  <pre><code>    var formdata = new FormData();
      formdata.append("uploadfilename", file);
      formdata.append("inte", ticketid);
      formdata.append("username", userName);
      formdata.append("custname", custName);
      formdata.append("userlastname", userLastName);
      formdata.append("par", par);
      formdata.append("mod", mod);
  
      var ajax = new XMLHttpRequest();
      ajax.upload.addEventListener("progress", progressHandler, false); 
      ajax.addEventListener("load", completeHandler, false);
      ajax.addEventListener("error", errorHandler, false);
      ajax.addEventListener("abort", abortHandler, false);
      ajax.open("POST", "mod/intern/uploader_upload_done.php", false);
      ajax.send(formdata);
  
      var response = JSON.parse(ajax.responseText);
      // parsing response
      ....
  
  
      function progressHandler(event)
      {
         var percent = 100 *(event.loaded / event.total);
         _("fortschritt").value = Math.round(percent);
         _("fortschritt_txt").innerHTML = Math.round(percent)+"% done...";
      }
  
  
      function completeHandler(event)
      { 
        _("fortschritt_txt").innerHTML = event.target.responseText;
        _("fortschritt").value = 100;
       _("ticketid").value = '';
     }
  
  
     function errorHandler(event)
     { 
        _("fortschritt_txt").innerHTML = "Upload failed";
     } 
  
  
      function abortHandler(event)
      {
        _("fortschritt_txt").innerHTML = "Upload cancelled";
      }
  </code></pre>