title: daterangepicker callback isn't work at all
body: <p>I have big trouble to run the callback function of my daterangepicker (from <a href="http://tamble.github.io/jquery-ui-daterangepicker/" rel="nofollow">http://tamble.github.io/jquery-ui-daterangepicker/</a>)</p>
  
  <p>I didn't see any alert.</p>
  
  <p>I have an 'apply' button at the bottom of the  daterangepicker  UI. I press apply and then fisld host date i've selected but no alert as it should show.</p>
  
  <p>This is the code I've done (really simple code):</p>
  
  <pre><code>// will host dates in callback
                  var startDate;
                  var endDate;
                  $('#daterangepicker').daterangepicker(
                    {
                        format: 'YYYY-MM-DD',
                        startDate: '2013-01-01',
                        endDate: '2013-12-31'
                    },
                    function (start, end) {
                        alert("hey");
                    }
                  );
  </code></pre>
  
  <p>Thanks in advance to help me</p>
  
  <p><strong>EDIT:</strong></p>
  
  <pre><code>// will host dates
                  var startDate;
                  var endDate;
                  // Show multidatetime picker
                  // more infos here: http://tamble.github.io/jquery-ui-daterangepicker/
                  $('#daterangepicker').daterangepicker(
                    {
                        onChange: function (start, end) { alert('change : ' + start + ' - ' + end) },
                        format: 'YYYY-MM-DD',
                        startDate: '2013-01-01',
                        endDate: '2013-12-31'
                    }
                  );
  </code></pre>
  
  <p>This is what I've tested but startDate and endDate are undefined.</p>
  
  <p><strong>EDIT 2 :</strong>
  This is my final code 100%working with the help of EricMathieu</p>
  
  <pre><code>// Show multidatetime picker
                  // more infos here: http://tamble.github.io/jquery-ui-daterangepicker/
                  $('#daterangepicker').daterangepicker(
                    {
                        format: 'YYYY-MM-DD',
                        startDate: '2013-01-01',
                        endDate: '2013-12-31'
                    });
  ...
  var tempValues = JSON.parse($('#daterangepicker').val());
  alert(tempValues.start);
  alert(tempValues.end);
  </code></pre>