text: var toggle = true;
  
  function toggleDataLabels(chart) {
      $.each(chart.series, function (i, el) {
          el.update({
              dataLabels: {
                  enabled: toggle
              }
          }, false);
  
      });
      toggle = !toggle;
      chart.redraw();
  }
  $(function () {
      var ids = ['a', 'b', 'c'],
          series = [],
          i = 0;
  
  
      for (; i < 3; i += 1) {
          series[i] = {
              data: [Math.random(), Math.random()],
              id: ids[i]
          }
      }
      for (; i < 9; i += 1) {
          series[i] = {
              data: [Math.random(), Math.random()],
              linkedTo: ids[i % 3]
          }
      }
  
      var chart = new Highcharts.Chart({
          chart: {
              renderTo: 'container'
          },
          title: {
              text: 'Linked series bug'
          },
          subtitle: {
              text: 'Series.update caused the last series to become unlinked'
          },
          series: series
      });
  });