Chart.JS tooltip callbacks label and title (v3.5)

(Please note: There are lots of answers for v2, this is for v3)

I’m trying to setup tooltips label and title for a doughnut chart.

Code:

        //Create the donut chart
    donut = new Chart('questions_positivity_donut', {
        type: 'doughnut',
        data: { 
            labels: ["Positive", "Other"],
            datasets: [{
                label: 'Sentiment',
                data: [user_context.state.avg_joy, (1-user_context.state.avg_joy)],
                backgroundColor: ['#a9a9a9','#f2f2f2']
            }]
        },
        options: {
            cutout: "70%",
            plugins: {
                legend: {
                    display: false
                },
                maintainAspectRatio: false,
                responsive: true,
                tooltip: {
                    callbacks: {
                        label: function(context) {

                            let label = new Intl.NumberFormat('en-US', {style: 'percent', minimumFractionDigits: 0, maximumFractionDigits: 0}).format(context.formattedValue);
                            return label;
                        },
                        title: function(context) {

                            let title = context.parsed.x;
                            return title;
                        } 
                    },
                    displayColors: false
                }                   
            }
        }
    });

JavaScript
​x
 
        //Create the donut chart
    donut = new Chart('questions_positivity_donut', {
        type: 'doughnut',
        data: { 
            labels: ["Positive", "Other"],
            datasets: [{
                label: 'Sentiment',
                data: [user_context.state.avg_joy, (1-user_context.state.avg_joy)],
                backgroundColor: ['#a9a9a9','#f2f2f2']
            }]
        },
        options: {
            cutout: "70%",
            plugins: {
                legend: {
                    display: false
                },
                maintainAspectRatio: false,
                responsive: true,
                tooltip: {
                    callbacks: {
                        label: function(context) {
​
                            let label = new Intl.NumberFormat('en-US', {style: 'percent', minimumFractionDigits: 0, maximumFractionDigits: 0}).format(context.formattedValue);
                            return label;
                        },
                        title: function(context) {
​
                            let title = context.parsed.x;
                            return title;
                        } 
                    },
                    displayColors: false
                }                   
            }
        }
    }); 
​

The label now works, and displays the value of the data, but the title is returning blank, instead of returning the label of the data (“Positive” or “Other”).

How can I return the correct title in the tooltip.callback?

Example: “Positive 35%” and “Other 65%”

Answer

If you log the context you could see its an array containing objects, with the default interaction mode you are using it only contains a single item so you can select that one and then access the label attribute on it like so:

var options = {
  type: 'doughnut',
  data: {
    labels: ["Red", "Blue", "Yellow", "Green", "Purple", "Orange"],
    datasets: [{
      label: '# of Votes',
      data: [12, 19, 3, 5, 2, 3],
      backgroundColor: ["Red", "Blue", "Yellow", "Green", "Purple", "Orange"]
    }]
  },
  options: {
    plugins: {
      tooltip: {
        callbacks: {
          label: function(context) {

            let label = new Intl.NumberFormat('en-US', {
              style: 'percent',
              minimumFractionDigits: 0,
              maximumFractionDigits: 0
            }).format(context.formattedValue);
            return label;
          },
          title: function(context) {
            let title = context[0].label;
            return title;
          }
        },
      }
    }
  }
}

var ctx = document.getElementById('chartJSContainer').getContext('2d');
new Chart(ctx, options);

JavaScript
 
var options = {
  type: 'doughnut',
  data: {
    labels: ["Red", "Blue", "Yellow", "Green", "Purple", "Orange"],
    datasets: [{
      label: '# of Votes',
      data: [12, 19, 3, 5, 2, 3],
      backgroundColor: ["Red", "Blue", "Yellow", "Green", "Purple", "Orange"]
    }]
  },
  options: {
    plugins: {
      tooltip: {
        callbacks: {
          label: function(context) {
​
            let label = new Intl.NumberFormat('en-US', {
              style: 'percent',
              minimumFractionDigits: 0,
              maximumFractionDigits: 0
            }).format(context.formattedValue);
            return label;
          },
          title: function(context) {
            let title = context[0].label;
            return title;
          }
        },
      }
    }
  }
}
​
var ctx = document.getElementById('chartJSContainer').getContext('2d');
new Chart(ctx, options);

<body>
  <canvas id="chartJSContainer" width="600" height="400"></canvas>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/3.5.1/chart.js"></script>
</body>

JavaScript
 
<body>
  <canvas id="chartJSContainer" width="600" height="400"></canvas>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/3.5.1/chart.js"></script>
</body>

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Answer