The feature to disable legend click in Chart.js does not activate unless the specific condition is met

Question

The feature to disable legend click in Chart.js does not activate unless the specific condition is met

I am working with chartjs and have encountered a scenario where I need to disable actions when a legend item is clicked, but only under certain conditions. I was able to accomplish this using the following code snippet:

legend: {
    position: 'right',
    onClick: (e) => {
      if (!this.isFilterView)
        e.stopPropagation();
},

However, when the filter view is active, I want the legend items to function as usual when clicked. The current code does not provide this functionality. Is there a way to achieve this?

javascript html css typescript chart.js

Answer 1

Answer №1

It seems like your legend.onClick function is overriding the default function, which is why stopping event propagation doesn't work.

The Chart.js documentation provides code snippets in the section "Custom On Click Actions" that mention explicitly invoking the default onClick function to achieve default behavior. Here's how you can modify your code:

var defaultLegendClickHandler = Chart.defaults.global.legend.onClick;
...
legend: {
  position: 'right',
  onClick: (event, legendItem) => {
    if (this.isFilterView) {
      defaultLegendClickHandler(event, legendItem);
    }
  },

However, if this doesn't work, you can manually toggle the hidden state of the datasets based on the value of isFilterView.

legend: {      
  onClick: (event, legendItem) => {
    if (this.isFilterView) {
      myChart.getDatasetMeta(legendItem.datasetIndex).hidden = !legendItem.hidden;
      myChart.update();
    }
  }
},

An example code snippet is provided below that demonstrates how this functionality operates. You can toggle the isFilterView variable using a checkbox at the top left of the canvas.

var isFilterView = false;

var myChart = new Chart('chart', {
  type: 'bar',
  data: {
    labels: ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday'],
    datasets: [{
        label: 'John Doe',
        data: [1, 2, 3, 4, 5],
        backgroundColor: 'red'
      },
      {
        label: 'Jane Clark',
        data: [5, 4, 3, 2, 1],
        backgroundColor: 'blue'
      },
      {
        label: 'Michael Smith',
        data: [3, 4, 2, 1, 5],
        backgroundColor: 'green'
      }
    ]
  },
  options: {
    legend: {      
      onClick: (event, legendItem) => {
        if (isFilterView) {
          myChart.getDatasetMeta(legendItem.datasetIndex).hidden = !legendItem.hidden;
          myChart.update();
        }
      }
    },
    scales: {
      yAxes: [{
        ticks: {
          beginAtZero: true,
          stepSize: 1
        }
      }],
    }
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.3/Chart.min.js"></script>
<input id="filterToggle" type="checkbox" onclick='isFilterView = !isFilterView;'>Filter View
<canvas id="chart" height="80"></canvas>

Answer 2

It seems like your legend.onClick function is overriding the default function, which is why stopping event propagation doesn't work.

The Chart.js documentation provides code snippets in the section "Custom On Click Actions" that mention explicitly invoking the default onClick function to achieve default behavior. Here's how you can modify your code:

var defaultLegendClickHandler = Chart.defaults.global.legend.onClick;
...
legend: {
  position: 'right',
  onClick: (event, legendItem) => {
    if (this.isFilterView) {
      defaultLegendClickHandler(event, legendItem);
    }
  },

However, if this doesn't work, you can manually toggle the hidden state of the datasets based on the value of isFilterView.

legend: {      
  onClick: (event, legendItem) => {
    if (this.isFilterView) {
      myChart.getDatasetMeta(legendItem.datasetIndex).hidden = !legendItem.hidden;
      myChart.update();
    }
  }
},

An example code snippet is provided below that demonstrates how this functionality operates. You can toggle the isFilterView variable using a checkbox at the top left of the canvas.

var isFilterView = false;

var myChart = new Chart('chart', {
  type: 'bar',
  data: {
    labels: ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday'],
    datasets: [{
        label: 'John Doe',
        data: [1, 2, 3, 4, 5],
        backgroundColor: 'red'
      },
      {
        label: 'Jane Clark',
        data: [5, 4, 3, 2, 1],
        backgroundColor: 'blue'
      },
      {
        label: 'Michael Smith',
        data: [3, 4, 2, 1, 5],
        backgroundColor: 'green'
      }
    ]
  },
  options: {
    legend: {      
      onClick: (event, legendItem) => {
        if (isFilterView) {
          myChart.getDatasetMeta(legendItem.datasetIndex).hidden = !legendItem.hidden;
          myChart.update();
        }
      }
    },
    scales: {
      yAxes: [{
        ticks: {
          beginAtZero: true,
          stepSize: 1
        }
      }],
    }
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.3/Chart.min.js"></script>
<input id="filterToggle" type="checkbox" onclick='isFilterView = !isFilterView;'>Filter View
<canvas id="chart" height="80"></canvas>

The feature to disable legend click in Chart.js does not activate unless the specific condition is met

Answer №1

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