Chart.js 3.7.1 - How can I control the number of ticks on the y axis of a line chart?

Question

The data will always be integers between -10 and 10, including 0 so there could be a maximum of 21 'intervals' on the y axis.
Regardless of the data, I need the y axis to display from -10 to 10 (including 0) in increments of 1. So I need a total of 21 (ticks?) on the y axis regardless of the data.

I tried this, per the docs: I also tried it without the steps param:

options: {
    scales: {
        y: {
            max: -10,
            min: 10,                    
            ticks: {
                steps: 21,
                stepSize: 1
            }
        }
    }
}

This is what I got:

Answer 1

The missing part in your code is autoSkip: false.

y: {
  max: 10,
  min: -10,
  ticks: {
    stepSize: 1,
    autoSkip: false
  }
}

According to the Chart.js documentation, autoskip is true by default.

autoskip: If true, automatically calculates how many labels can be shown and hides labels accordingly. (...) Turn autoSkip off to show all labels no matter what.

Please take a look at below runnable code and see how it works.

new Chart('canvas', {
  type: 'line',
  data: {
    labels: ['A', 'B', 'C', 'D', 'E', 'F'],
    datasets: [{
        label: 'Dataset 1',
        data: [3, 9, 7, 5, 9, 2],
        backgroundColor: 'rgba(255, 99, 132, 0.2)',
        borderColor: 'rgb(255, 99, 132)',
        fill: false
      },
      {
        label: 'Dataset 2',
        data: [1, 2, -3, -5, -2, 1],
        backgroundColor: 'rgba(255, 159, 64, 0.2)',
        borderColor: 'rgb(255, 159, 64)'
      }
    ]
  },
  options: {
    scales: {
      y: {
        max: 10,
        min: -10,
        ticks: {
          stepSize: 1,
          autoSkip: false
        }
      }
    }
  }
});

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