How to add an extra tick on top of the highest bar in Chart.js v2.9.4 (grace)?

Question

I would like to know how to add an extra tick on top of the highest bar in Chartjs.
I don't like the way that the graph just stops after 25 (see image), I would like it to stop at one tick more (in this example 30). The reason that I'm using V2.9.4 is because I am using it in Nuxt with the Vuejs version of Chartjs.
I did find out that in the newest versions of Chartjs its called grace.
I couldn't really find an answer on my question with the V2.9.4 version of Chartjs.
Code isn't really relevant but still included it.

BarChart.vue (component)

    <script>
    import {Bar} from "vue-chartjs";
    
    export default {
      extends: Bar,
      props: {
        data: {
          type: String,
          default: () => {},
        },
        options: {
          type: Object,
          default: () => {},
        },
      },
      computed: {
        Chart() {
          return['data', 'options'];
        },
      },
      mounted() {
        this.renderChart(this.data, this.options);
      },
    };
    </script>

HTML:

    <div class="chart">
      <BarChart :data="barChartData" :options="barChartOptions" :height="200"/>
    </div>

Script:

    <script>
    import BarChart from "~/components/plugins/BarChart";
    
    export default {
      components: {
        BarChart,
      },
      data() {
        return {
          barChartData: {
            labels: ["Verzonden", "Ontvangen", "Geopend", "Kliks"],
            datasets: [
              {
                data: [25, 20, 20, 18],
                backgroundColor: [
                  '#7782FF',
                  '#403DD3',
                  '#FFB930',
                  '#00E437',
                ],
                barThickness : 50,
              },
            ],
          },
          barChartOptions: {
            responsive: true,
            plugins: {
              customScale: {
                grace: '100%',
              },
            },
            legend: {
              display: false,
            },
            scales: {
              xAxes: [
                {
                  gridLines: {
                    display: false,
                  },
                  ticks: {
                    fontColor: "black",
                    fontSize: 14,
                  },
                },
              ],
              yAxes: [
                {
                  ticks: {
                    beginAtZero: true,
                    min: 0,
                    stepSize: 5,
                    fontColor: '#ABACB3',
                  },
                  gridLines: {
                    display: true,
                    borderDash: [4, 4],
                    color: '#EEEDFB',
                    drawBorder: false,
                  },
                },
              ],
            },
          },
        };
      },
    };
    </script>

This is how it looks now

This is how I want it to look

Thanks in advance. :)

Answer 1

You can use a custom plugin to achieve this:

const options = {
  type: 'bar',
  data: {
    labels: ["Red", "Blue", "Yellow", "Green", "Purple", "Orange"],
    datasets: [{
        label: '# of Votes',
        data: [12, 20, 3, 5, 2, 3],
        borderWidth: 1
      },
      {
        label: '# of Points',
        data: [7, 11, 5, 8, 3, 7],
        borderWidth: 1
      }
    ]
  },
  options: {
    plugins: {
      customScale: {
        grace: '100%', // Percentage of max value
        // grace: 40 // Flatout extra value to add
      }
    }
  },
  plugins: [{
    id: "customScale",
    beforeLayout: (chart, options, c) => {
      let max = Number.MIN_VALUE;
      let min = Number.MAX_VALUE
      let grace = options.grace || 0

      chart.data.datasets.forEach((dataset) => {
        max = Math.max(max, Math.max(...dataset.data));
        min = Math.min(min, Math.min(...dataset.data))
      })

      if (typeof grace === 'string' && grace.includes('%')) {
        grace = Number(grace.replace('%', '')) / 100

        chart.options.scales.yAxes[0].ticks.suggestedMax = max + (max * grace)
        chart.options.scales.yAxes[0].ticks.suggestedMin = min - (min * grace)

      } else if (typeof grace === 'number') {

        chart.options.scales.yAxes[0].ticks.suggestedMax = max + grace
        chart.options.scales.yAxes[0].ticks.suggestedMin = min - grace

      }

    }
  }]
}

const 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/2.9.4/Chart.js"></script>
</body>

EDIT:

I assume the 'BarChart' is a wrapper component from an external lib in which case you need to pass the plugin to it. I guess it has to be done like so but you might need to check the documentation of the specific wrapper you are using:

<BarChart :data="barChartData" :options="barChartOptions" :plugins="[plugin]" :height="200"/>

const plugin = {
  id: "customScale",
  beforeLayout: (chart, options, c) => {
    let max = Number.MIN_VALUE;
    let min = Number.MAX_VALUE
    let grace = options.grace || 0

    chart.data.datasets.forEach((dataset) => {
      max = Math.max(max, Math.max(...dataset.data));
      min = Math.min(min, Math.min(...dataset.data))
    })

    if (typeof grace === 'string' && grace.includes('%')) {
      grace = Number(grace.replace('%', '')) / 100

      chart.options.scales.yAxes[0].ticks.suggestedMax = max + (max * grace)
      chart.options.scales.yAxes[0].ticks.suggestedMin = min - (min * grace)

    } else if (typeof grace === 'number') {

      chart.options.scales.yAxes[0].ticks.suggestedMax = max + grace
      chart.options.scales.yAxes[0].ticks.suggestedMin = min - grace

    }

  }
}