title: how to get index of a point in Highcharts to use in an event?
body: <p>In a Highcharts chart I want to know index of a point when clicking over it. 
  The following code (<a href="https://jsfiddle.net/9bwmrogg/1/" rel="nofollow">here</a> jfiddle version) does not work: </p>
  
  <pre><code>$(function () {
      $('#container').highcharts({
          xAxis: {
              categories: ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']
          },
  
          plotOptions: {
              series: {
                  cursor: 'pointer',
                  point: {
                      events: {
                          click: function () {
                              alert('Category: ' + this.category + ', value: ' + this.y+ ', index: ' + this.indexOf);
                          }
                      }
                  }
              }
          },
  
          series: [{
              data: [29.9, 71.5, 106.4, 129.2, 144.0, 176.0, 135.6, 148.5, 216.4, 194.1, 95.6, 54.4]
          }]
      });
  });
  </code></pre>
  
  <p><a href="https://stackoverflow.com/questions/8507673/how-to-get-index-of-a-point-in-highcharts">Elsewhere</a> it is suggested to use indeOf, as I have done, but it seems to work only in formatter tooltip section. What's wrong?</p>