How can I hide legend text if it's zero?

Question

I'm trying to hide the legend title of an item, if it's value is zero. There are similar problems existing here, but nothing led to solving my problem.

Below is my source code:

<script>
      var ctx = document.getElementById('beratungsfelderChart');
      var myDoughnutChart = new Chart(ctx, {
        type: 'doughnut',
        data: {
            labels: ['Group A', 'Group B', 'Group C', 'Group D', 'Group E'],
            datasets: [{
                label: '# of Votes',
                data: [0, 3, 3, 5, 2],
                backgroundColor: [
                    '#172b4dD9',
                    '#2dce89D9',
                    '#231F20D9',
                    '#192d35D9',
                    '#3B6058D9'
                ]
            }]
        },
        options: {
          legend: {
            labels: {
              //filter: function(item, chart, context) {
              //  return !item.text.includes('Test');
              //}
              filter: function(item, context) {
                return !context.dataset.data[context.dataIndex] == 0;
              } 
            }
          },
          axis: {
            scales: {
                yAxes: [{
                    display: false
                }],
                xAes: [{
                  ticks: {
                    display: false
                  }
                }]
            }
          },
          plugins: {
            datalabels: {
              display: function(context) {
                return context.dataset.data[context.dataIndex] > 1;
              }
            }
          }
        }
    });

    </script>

As you can see I tried a few potential solutions, but until now, nothing worked out unfortunately.
1. options -> legend -> labels
2. options -> plugins -> datalabels

I hope that someone can help me somehow.

Best, Nader

Answer 1

You can also use generateLabels instead of filter. it's a newer method and you would be able to change value and style of each legends. For example I've removed zero values and added data to each label :

new Chart(document.getElementById('beratungsfelderChart'), {
  type: 'doughnut',
  data: {
    labels: ['Group A', 'Group B', 'Group C', 'Group D', 'Group E'],
    datasets: [{
      label: '# of Votes',
      data: [0, 3, 3, 5, 2],
      backgroundColor: [
        '#192d35',
        '#36A2EB',
        '#FFCE56',
        '#FF6384',
        '#3B6058'
      ]
    }]
  },
  options: {
    legend: {
      labels: {
          generateLabels: function (chart) {
                var newLegends = [];
                chart.data.labels.forEach(function (label, index) {
                    if (chart.data.datasets[0].data[index] == 0) //zero values
                        return;
                    var legend = {
                        text: label + ' ('+chart.data.datasets[0].data[index]+')',
                        fillStyle: chart.data.datasets[0].backgroundColor[index]
                    };
                    newLegends.push(legend)
                });

                return newLegends;
            }
      }
    },
    axis: {
      scales: {
        yAxes: [{
          display: false
        }],
        xAes: [{
          ticks: {
            display: false
          }
        }]
      }
    }
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.3/Chart.bundle.js"></script> 
<canvas id="beratungsfelderChart" height="90"></canvas>

Answer 2

You should use legend.labels.filter as follows.

legend: {
  labels: {
    filter: (legendItem, data) => data.datasets[0].data[legendItem.index] != 0
  }
}

new Chart(document.getElementById('beratungsfelderChart'), {
  type: 'doughnut',
  data: {
    labels: ['Group A', 'Group B', 'Group C', 'Group D', 'Group E'],
    datasets: [{
      label: '# of Votes',
      data: [0, 3, 3, 5, 2],
      backgroundColor: [
        '#172b4dD9',
        '#2dce89D9',
        '#231F20D9',
        '#192d35D9',
        '#3B6058D9'
      ]
    }]
  },
  options: {
    legend: {
      labels: {
        filter: (legendItem, data) => data.datasets[0].data[legendItem.index] != 0
      }
    },
    axis: {
      scales: {
        yAxes: [{
          display: false
        }],
        xAes: [{
          ticks: {
            display: false
          }
        }]
      }
    }
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.3/Chart.bundle.js"></script> 
<canvas id="beratungsfelderChart" height="90"></canvas>