title: Apex Charts tooltip formatter: how to convert number to string
body: <p>I am trying to show y value of a line graph in tooltips (apexcharts). The original data is set in string format in series {'8:50 AM', '11:00 AM', '9:02 AM'...}, but they appear as '8', '11', '9'... in tooltips, rounded up in number format. I do not understand why the string data is converted and rounded by itself. I used 'toString' to reveal the full text ('8:50 AM', '11:00 AM', '9:02 AM'...) in the tooltip formatter, but it did not work. Any suggestion?</p>
  
  <pre><code>var spark1 = {
    chart: {
      id: 'sparkline1',
      type: 'line',
      height: 200,
      sparkline: {
        enabled: true
      },
      group: 'sparklines'
    },
    series: [{
      name: 'wake-up time',
      data: [{x: '05/06/2014', y:'8:50 AM'}, {x: '05/07/2014', y:'11:00 AM'}, {x: '05/08/2014', y:'9:02 AM'}, {x: '05/09/2014', y:'10:47 AM'}]
    }],
    tooltip: {
      x: {
        show: false
      },
      y: {
        formatter: function(value){
        return value.toString();
         }
      }
    }
   }
  }
  </code></pre>