title: collect multiple inputs file to append to FormData
body: <p>Suppose I have the following form.</p>
  
  <pre><code>&lt;form id="testForm"&gt;
    &lt;input type="file" name="uploads[]"&gt;&lt;br/&gt;
    &lt;input type="file" name="uploads[]"&gt;&lt;br/&gt;
    &lt;input type="file" name="uploads[]"&gt;&lt;br/&gt;
    &lt;input type="submit"&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>And this is part of the submit code which tries to collect files to append to FormData, but I don't know how to do it properly.</p>
  
  <pre><code>var formData = new FormData();
  
  var fileList = $("input[name='uploads[]']");
  for(var x = 0; x &lt; fileList.length; x++) {
    formData.append('file'+x, ???);
    console.log('appended a file');
  }
  
  var request = new XMLHttpRequest();
  request.open('POST', '/upload');
  request.send(formData);
  
  request.onload = function(e) {
    console.log('Request Status', request.status);
  };
  </code></pre>
  
  <p>This is the server code.</p>
  
  <pre><code>app.post('/upload', function(req, res) {
    var form = new formidable.IncomingForm();
    form.parse(req, function(err, fields, files) {
      console.log('handling form upload - fields', fields);
      console.log('handling form upload - files', files);
    });
    res.send('Thank you');
  });
  </code></pre>
  
  <p>If it works, I expect to see output and files saved in /tmp.</p>