title: How do I manipulate a specific tooltip value of a Chart.js pie chart?
body: <p>I'm successfully displaying a Pie chart from <code>Chart.js</code>. If I hover the given slice, it will also return the label, as well as the value.</p>
  
  <p>However, the value isn't very user friendly; I'd like to convert it to another value, more comprehensible for users.</p>
  
  <p>How do I access the tooltip value for one given slice? I can only seem to get them all.</p>
  
  <p>Sample code:</p>
  
  <pre><code>    this.examplePieChart  = new Chart(ctx1,{
          type: 'pie',
          data: {
              labels: byteLabels,
              datasets: [
                  {
                      label: 'bytes',
                      data: BytesArr,
                      backgroundColor: defaultChartColors,
                  },
              ]
          },
          options: {
              tooltips: {
                  mode: 'label',
              }   
          }
      });
  </code></pre>
  
  <p>I can access ALL the values of the tooltip data, my attempt was something like this:</p>
  
  <pre><code>            tooltips: {
                  mode: 'label',
                  callbacks: {
                      label: function (tooltipItem, data) {
                          let tmpArr = [];
                          for(let i = 0; i &lt; data.datasets[0].data.length; i++){
                              tmpArr.push(data.datasets[0].data[i].fileSize());
                          }
                          return tmpArr;
                      }
                  }
              }
  </code></pre>
  
  <p>Where i run the <code>fileSize()</code> to convert Bytes to MiB/KiB. And it works - however, when hovering a slice, it will show ALL tooltips on any given slice, instead of the one I'm hovering.</p>
  
  <p>How do I access the data value of a single given slice of a pie chart, and manipulate it? Currently, I can only access them all with the <code>data</code> value, which returns an entire array. </p>
  
  <p>Without the callback above, I am successfully showing <code>label: value</code>, but I want to manipulate this specific value for each slice - not all values at once :o)</p>