它几乎看起来像是文档的例子是错误的，似乎他们没有给予图表，这就是为什么它失败，如果你自己提供图表，并编写完整的onclick它确实工作
范例：

const defaultLegendClickHandler = Chart.defaults.global.legend.onClick;
var newLegendClickHandler = function(e, legendItem) {
  alert(legendItem.text)
  const index = legendItem.index;
  const {
    type
  } = chart.config;
  if (type === 'pie' || type === 'doughnut') {
    // Pie and doughnut charts only have a single dataset and visibility is per item
    for (i = 0, ilen = (chart.data.datasets || []).length; i < ilen; ++i) {
      meta = chart.getDatasetMeta(i);
      // toggle visibility of index if exists
      if (meta.data[index]) {
        meta.data[index].hidden = !meta.data[index].hidden;
      }
    }
  } else {
    const index = legendItem.datasetIndex;
    const ci = this.chart;
    const meta = ci.getDatasetMeta(index);
    // See controller.isDatasetVisible comment
    meta.hidden = meta.hidden === null ? !ci.data.datasets[index].hidden : null;
    // We hid a dataset ... rerender the chart
    ci.update();
  }
  chart.update();
};
const options = {
  type: 'pie',
  data: {
    labels: ["Red", "Blue", "Yellow", "Green", "Purple", "Orange"],
    datasets: [{
      label: '# of Votes',
      data: [12, 19, 3, 5, 2, 3],
      borderWidth: 1
    }, {
      label: '# of Votes2',
      data: [12, 19, 3, 5, 2, 3],
      borderWidth: 1
    }, {
      label: '# of Votes3',
      data: [12, 19, 3, 5, 2, 3],
      borderWidth: 1
    }, {
      label: '# of Votes4',
      data: [12, 19, 3, 5, 2, 3],
      borderWidth: 1
    }]
  },
  options: {
    legend: {
      onClick: newLegendClickHandler
    }
  }
}
const ctx = document.getElementById('chartJSContainer').getContext('2d');
const chart = new Chart(ctx, options);

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您可以通过使用以下行更新图例来更新图例onClick。

@ViewChild('barChart') barChart: BaseChartDirective;
legend: {
    labels: {
    onClick: (event, barLegendItem, legend) => {
      const datasetIndex = barLegendItem.datasetIndex;
      const scatterDataset = this.barChartData.datasets[datasetIndex - this.noOfInnings];
      const barDataset = this.barChartData.datasets[datasetIndex];
      scatterDataset.hidden = !scatterDataset.hidden;
      barDataset.hidden = !barDataset.hidden;
      legend.chart.update(this.barChart);
    }
  }
HTML :
canvas id="chart1" class="w-100 h-100" baseChart
            #barChart
            [data]="barChartData"
            [options]="barChartOptions"
            [plugins]="barChartPlugins"
            [legend]="barChartLegend">
    </canvas>

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