[Chartjs]-How add the sizes of the slices in the pie chart (at the top) in Chart.js?

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0👍

✅

I found the answer. My project is written in CoffeeScript, but I think it would be more useful for the StackOverflow community to post the code in JS.

options: {
  legend: {
    labels: {
      generateLabels: function(chart) {
        var data = chart.data;
        if (data.labels.length && data.datasets.length) {
          return data.labels.map(function(label, i) {
            var meta = chart.getDatasetMeta(0);
            var ds = data.datasets[0];
            var arc = meta.data[i];
            var custom = arc && arc.custom || {};
            var getValueAtIndexOrDefault = Chart.helpers.getValueAtIndexOrDefault;
            var arcOpts = chart.options.elements.arc;
            var fill = custom.backgroundColor ? custom.backgroundColor : getValueAtIndexOrDefault(ds.backgroundColor, i, arcOpts.backgroundColor);
            var stroke = custom.borderColor ? custom.borderColor : getValueAtIndexOrDefault(ds.borderColor, i, arcOpts.borderColor);
            var bw = custom.borderWidth ? custom.borderWidth : getValueAtIndexOrDefault(ds.borderWidth, i, arcOpts.borderWidth);
            var value = chart.config.data.datasets[arc._datasetIndex].data[arc._index];

            return {
                text: label + ": " + value,
                fillStyle: fill,
                strokeStyle: stroke,
                lineWidth: bw,
                hidden: isNaN(ds.data[i]) || meta.data[i].hidden,
                index: i
            };
          });
        } else {
          return [];
        }
      }
    }
  }
}

0👍

You can use the plugin system for this:

var options = {
  type: 'pie',
  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: {
      customNumber: {
        textColor: 'red',
        xOffset: 10,
        yOffset: 0,
        font: '24px  Comic Sans MS'
      }
    }
  },
  plugins: [{
    id: 'customNumber',
    afterDraw: (chart, args, opts) => {
      const hoveredSlice = chart._active[0];
      const {
        ctx,
        chartArea: {
          right
        }
      } = chart;

      if (!hoveredSlice) {
        return;
      }

      ctx.font = opts.font || '24px verdana, sans-serif'
      ctx.fillStyle = opts.textColor || 'black'

      const val = chart.data.datasets[hoveredSlice.datasetIndex].data[hoveredSlice.index];
      const meassures = ctx.measureText(val);
      const height = ctx.measureText('M').width;

      ctx.fillText(val, (right - meassures.width - (opts.xOffset || 0)), height + (opts.yOffset || 0))
    }
  }]
}

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/3.6.0/chart.js"></script>
</body>

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