Chart.js: grid lines only on dataset points - grid

Question

I created a simple chart:
const myChart = new Chart(document.getElementById('myChartChart').getContext('2d');, {
type: 'scatter',
data: {
datasets: [{
label: 'Dataset',
data: [{
x: -40,
y: 34,
}, {
x: -10,
y: 45,
}, {
x: 140,
y: 45,
}],
fill: true,
stepped: true,
}]
},
options: {
responsive: true,
scales: {
x: {
suggestedMin: -50,
suggestedMax: 150,
ticks: {
callback: function(value, index, values) {
return value + ' °C';
}
},
},
y: {
suggestedMin: 32,
suggestedMax: 46,
ticks: {
callback: function(value, index, values) {
return value + ' bar';
}
},
}
},
plugins: {
legend: {
display: false
}
}
}
});
Fiddle: https://jsfiddle.net/o6b97xL2
But I don't like to have static periodical grid lines and labels but only on my three data points.
With callbacks I only get the defined steps from the grid. How can I achieve something like this:
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Answer 1

You can define afterBuildTicks callbacks on both axes. In there, you replace the axis ticks with your own ticks extracted from your data.
Please take a look at your amended code and see how it works.
const data = [
{ x: -40, y: 34 },
{ x: -10, y: 45 },
{ x: 140, y: 45 }
];
myChart = new Chart('myChartChart', {
type: 'scatter',
data: {
datasets: [{
label: 'Dataset',
data: data,
fill: true,
stepped: true,
}]
},
options: {
responsive: true,
scales: {
x: {
suggestedMin: -50,
suggestedMax: 150,
afterBuildTicks: axis => axis.ticks = data.map(v => ({ value: v.x })),
ticks: {
callback: v => v + ' °C'
}
},
y: {
suggestedMin: 32,
suggestedMax: 46,
afterBuildTicks: axis => axis.ticks = data.map(v => ({ value: v.y })),
ticks: {
callback: v => v + ' bar'
}
}
},
plugins: {
legend: {
display: false
}
}
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/3.6.2/chart.min.js"></script>
<canvas id="myChartChart"></canvas>