title: How to add to an existing FileList object with JavaScript?
body: <p>I am creating a drag and drop file upload zone. When I upload multiple files at a time it works but I need it to be able to support uploading in multiple stages. I know that the issue below is that I am setting files each time, but I can't figure out the right way to get more files added to dFiles each time the method is called</p>
  
  <pre><code>    var dFiles;
      //var dFiles = []
      var holder = document.getElementById('holder');
      holder.ondrop = function (e) {
          e.preventDefault();
          dFiles = (e.dataTransfer.files);
          //dFiles.push(e.dataTransfer.files);
     }
  </code></pre>
  
  <p>I tried initilaizing dfiles as an empty array and adding the files (commented out above). Later this created a data type mismatch error when I was reading the file data</p>
  
  <pre><code>for (var i = 0; i &lt; dFiles.length; i++) {
      reader = new FileReader();
      reader.readAsDataUrl(dFiles[i]); //error
  }
  </code></pre>