javascript - How to modify chartjs tooltip to can add customized strings in tooltips

Javascript - How to modify chartjs tooltip to can add customized strings in tooltips

To modify Chart.js tooltips and add customized strings, you can use the callbacks property in the options object when creating your chart. Specifically, you can use the label and afterLabel callback functions to customize the tooltips.

Here's an example:

<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>Customized Tooltips in Chart.js</title> <script src="https://cdn.jsdelivr.net/npm/chart.js"></script> </head> <body> <canvas id="myChart" width="400" height="200"></canvas> <script> const ctx = document.getElementById('myChart').getContext('2d'); const data = { labels: ['January', 'February', 'March', 'April', 'May'], datasets: [{ label: 'My Dataset', data: [10, 20, 15, 25, 30], backgroundColor: 'rgba(75, 192, 192, 0.2)', borderColor: 'rgba(75, 192, 192, 1)', borderWidth: 1, }] }; const options = { tooltips: { callbacks: { label: function (tooltipItem, data) { return 'Value: ' + tooltipItem.yLabel; }, afterLabel: function (tooltipItem, data) { return 'Custom String: This is a custom string'; }, }, }, }; const myChart = new Chart(ctx, { type: 'bar', data: data, options: options, }); </script> </body> </html>

In this example:

  • The label callback is used to customize the main content of the tooltip. In this case, it adds the label "Value: " before the actual data value.

  • The afterLabel callback is used to add a custom string after the main content. In this case, it adds the label "Custom String: This is a custom string" after the value.

You can customize the callbacks according to your specific needs. The tooltipItem parameter in the callbacks contains information about the tooltip, and you can use it to customize the tooltip content dynamically. Adjust the callback functions to suit your use case.

Examples

  1. "Add custom text to Chart.js tooltip"

    • Code:
      const chart = new Chart(ctx, { type: 'bar', data: {...}, options: { tooltips: { callbacks: { label: function (tooltipItem, data) { return 'Custom Text: ' + tooltipItem.yLabel; } } } } });
    • Description: Adds custom text to the Chart.js tooltip using the label callback.

  2. "Modify tooltip to display additional information"

    • Code:
      const chart = new Chart(ctx, { type: 'line', data: {...}, options: { tooltips: { callbacks: { label: function (tooltipItem, data) { return data.datasets[tooltipItem.datasetIndex].label + ': ' + tooltipItem.yLabel + ' Custom Info'; } } } } });
    • Description: Modifies the tooltip to display additional information along with the default label and value.

  3. "Customize tooltip title and body"

    • Code:
      const chart = new Chart(ctx, { type: 'radar', data: {...}, options: { tooltips: { callbacks: { title: function (tooltipItems, data) { return 'Custom Title'; }, label: function (tooltipItem, data) { return 'Value: ' + tooltipItem.yLabel; } } } } });
    • Description: Customizes both the tooltip title and body.

  4. "Add dynamic text to Chart.js tooltip"

    • Code:
      const chart = new Chart(ctx, { type: 'doughnut', data: {...}, options: { tooltips: { callbacks: { label: function (tooltipItem, data) { const dataset = data.datasets[tooltipItem.datasetIndex]; const total = dataset.data.reduce((previousValue, currentValue) => previousValue + currentValue); const percentage = Math.round((dataset.data[tooltipItem.index] / total) * 100); return dataset.label + ': ' + dataset.data[tooltipItem.index] + ' (' + percentage + '%)'; } } } } });
    • Description: Adds dynamic text to the tooltip, calculating and displaying percentages.

  5. "Display multiple lines in Chart.js tooltip"

    • Code:
      const chart = new Chart(ctx, { type: 'bar', data: {...}, options: { tooltips: { callbacks: { label: function (tooltipItem, data) { const dataset = data.datasets[tooltipItem.datasetIndex]; return [ 'Label: ' + dataset.label, 'Value: ' + tooltipItem.yLabel ]; } } } } });
    • Description: Displays multiple lines in the tooltip for each dataset.

  6. "Include dataset name in tooltip"

    • Code:
      const chart = new Chart(ctx, { type: 'line', data: {...}, options: { tooltips: { callbacks: { label: function (tooltipItem, data) { const dataset = data.datasets[tooltipItem.datasetIndex]; return 'Dataset: ' + dataset.label + ', Value: ' + tooltipItem.yLabel; } } } } });
    • Description: Includes the dataset name in the tooltip along with the value.

  7. "Format Chart.js tooltip with HTML"

    • Code:
      const chart = new Chart(ctx, { type: 'scatter', data: {...}, options: { tooltips: { callbacks: { title: function (tooltipItem, data) { return '<b>Custom Title</b>'; }, label: function (tooltipItem, data) { return 'Value: ' + tooltipItem.yLabel; } } } } });
    • Description: Formats the tooltip using HTML for both title and label.

  8. "Change tooltip font color and background"

    • Code:
      const chart = new Chart(ctx, { type: 'bar', data: {...}, options: { tooltips: { callbacks: {...}, backgroundColor: 'rgba(255, 0, 0, 0.7)', titleFontColor: '#ffffff', bodyFontColor: '#ffffff' } } });
    • Description: Changes the font color and background color of the tooltip.

  9. "Add custom prefix and suffix to Chart.js tooltip"

    • Code:
      const chart = new Chart(ctx, { type: 'pie', data: {...}, options: { tooltips: { callbacks: { label: function (tooltipItem, data) { return 'Prefix: ' + tooltipItem.yLabel + ' Suffix'; } } } } });
    • Description: Adds custom prefix and suffix to the tooltip value.

  10. "Display additional information in the tooltip using global tooltip customization"

    • Code:
      const chart = new Chart(ctx, { type: 'polarArea', data: {...}, options: { tooltips: { mode: 'index', intersect: false }, custom: function (tooltipModel) { // Customize tooltip here tooltipModel.title[0] = 'Custom Title: ' + tooltipModel.title[0]; tooltipModel.body[0].lines[0] = 'Value: ' + tooltipModel.body[0].lines[0]; } } });
    • Description: Customizes the tooltip globally using the custom function.

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