title: FileReader error: The object is already busy reading Blobs
body: <p>I'm making a drag-and-drop file upload system for photo gallery uploads. This is my source code handling dropped files. This one works multiple files if I drop them one by one it works but when I drop more than one at the same time this error occures:</p>
  
  <p><code>Uncaught InvalidStateError: Failed to execute 'readAsDataURL' on 'FileReader': The object is already busy reading Blobs.</code></p>
  
  <pre><code>function handleFiles(files)
  {
      var reader = new FileReader();
      var formdata = new FormData();
  
      $.each(files, function(i, j)
      {
          $("td.photos span.status").html("Processing file: "+j.name);
  
          formdata.append('file', j);
  
          $.ajax({
              url: "uploadalbum.php",
              type: "POST",
              dataType: "json",
              data: formdata,
              processData: false,
              contentType: false,
              success: uploadfinished
          });
  
          reader.onload = handleReaderLoad;
          reader.readAsDataURL(j);
      });
  }
  </code></pre>
  
  <p>Any ideas?</p>