title: How to cancel/abort upload in Dropzone.js if condition is not fulfilled?
body: <p>I'm using <a href="http://dropzonejs.com" rel="nofollow noreferrer">Dropzone.js</a> to upload files. Now I want to check a filed is filled or not, and if it isn't then cancel the upload.</p>
  <p>My HTML code:</p>
  <pre><code>&lt;input type=&quot;text&quot; name=&quot;title&quot; id=&quot;title&quot; placeholder=&quot;Type the title of the album&quot;&gt;
  &lt;form action=&quot;file-upload.cgi&quot; enctype=&quot;multipart/form-data&quot; class=&quot;dropzone&quot; id=&quot;dropzoneform&quot;&gt;&lt;/form&gt;
  </code></pre>
  <p>My jQuery code:</p>
  <pre><code>Dropzone.autoDiscover = false;
  $('.dropzone').dropzone({
      acceptedFiles: 'image/jpeg',
      init: function() {
          this.on('sending', function() {
              if ( $('#title').val().length &gt; 0 ) {
                  // just start automatically the uploading
              } else {
                  // need a code to cancel the uploading
              }
          });
      }
  });
  </code></pre>
  <p>How can I cancel the uploading when the <code>#title</code>'s length is 0?</p>