ChartJS Custom text on certain xAxis and yAxis linesS - chart.js

Question

See attached screenshot with an example with what I'm trying to do.
Basically I want to be able to add custom text on certain yAxis and xAxis lines.

Answer 1

You can use the Plugin Core API. It offers different hooks that may be used for executing custom code. In below code snippet, I use the afterDraw hook to draw custom text on the canvas.
For positioning your text on x and y, you may use hard coded number of pixels or compute them using the Scale Interface (i.e. function getPixelForValue).
new Chart(document.getElementById('myChart'), {
type: 'bar',
plugins: {
afterDraw: chart => {
var ctx = chart.chart.ctx;
var xAxis = chart.scales['x-axis-0'];
var yAxis = chart.scales['y-axis-0'];
ctx.save();
ctx.font = "18px Arial";
ctx.fillStyle = "red";
var x = (xAxis.getPixelForValue('May') + xAxis.getPixelForValue('June')) / 2;
ctx.fillText('My custom text here', x, yAxis.getPixelForValue(65));
ctx.fillText('Another custom text here', 30, 15);
ctx.restore();
}
},
data: {
labels: ['January', 'February', 'March', 'April', 'May', 'June', 'July'],
datasets: [{
label: "My First Dataset",
data: [65, 59, 80, 81, 56, 55, 40],
fill: false,
backgroundColor: ['rgba(255, 99, 132, 0.2)', 'rgba(255, 159, 64, 0.2)', 'rgba(255, 205, 86, 0.2)', 'rgba(75, 192, 192, 0.2)', 'rgba(54, 162, 235, 0.2)', 'rgba(153, 102, 255, 0.2)', 'rgba(201, 203, 207, 0.2)'],
borderColor: ['rgb(255, 99, 132)', 'rgb(255, 159, 64)', 'rgb(255, 205, 86)', 'rgb(75, 192, 192)', 'rgb(54, 162, 235)', 'rgb(153, 102, 255)', 'rgb(201, 203, 207)'],
borderWidth: 1
}]
},
options: {
scales: {
yAxes: [{
ticks: {
beginAtZero: true
}
}]
}
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.9.3/Chart.min.js"></script>
<canvas id="myChart" height="110"></canvas>