Change ChartJs axis title dynamically

Question

I've created a chart like this

if (userLanguageCode === "es") {
    customTooltipFormat = 'DD/MM/YYYY, HH:mm:ss';

    customDisplayFormats = {
        'millisecond': 'SSS [ms]',
        'second': 'HH:mm:ss', // 11:20:01 AM
        'minute': 'D/MM/YY HH:mm', // 11:20:01 AM
        'hour': 'D/MM/YY HH[h]', // Sept 4, 5PM
        'day': 'D/MM/YYYY', // Sep 4 2015
        'week': 'll', // Week 46, or maybe "[W]WW - YYYY" ?
        'month': 'MMM YYYY', // Sept 2015
        'quarter': '[Q]Q - YYYY', // Q3
        'year': 'YYYY', // 2015
    };
}

Chart.defaults.global.responsive = true;
Chart.defaults.global.animation = false;

datosChartHistoricos =  {
    labels: [],
    datasets: [{
        label: textoValor,
        backgroundColor: "rgba(0,181,255,0.5)",
        fill: chartWithIncrementValues? true: false,
        borderColor: "rgba(0,192,192,1)",
        pointBorderColor: "rgba(0,181,255,1)",
        pointBackgroundColor: "rgba(255,255,255,1)",
        pointBorderWidth: 1,
        data: []
    }]
};

var ctx = document.getElementById("grafica").getContext("2d");
chartHistoricos = new Chart(ctx, {
    type: chartWithIncrementValues? "bar" : "line",
    data: datosChartHistoricos,
    options: {
        responsive: true,
        elements: {
            rectangle: {
                borderWidth: 1,
                borderColor: 'rgb(0, 0, 0)',
                borderSkipped: 'bottom'
            }
        },
        scales: {
            xAxes: [{
                type: "time",
                time: {
                    tooltipFormat: customTooltipFormat,
                    displayFormats: customDisplayFormats,
                }
            }, ],
            yAxes: [{
                scaleLabel: {
                    display: true,
                    labelString: textoValor + " (" + unidadesValor + ")"
                }
            }]
        },
        legend: {
            display: false,
        }
    }
});

This is the default config for the chart, data is added dynamically, but the user can choose different data values to show, like temperature, distance... To do this, I just change the data value of the dataset and the label, but I can't figure how to change the yAxis label using javascript when I change the dataset value. Initialization title is ok.

Any tips?

Thanks!

Answer 1

You can change the scale title simply by updating the labelString value in your chart object's options property and calling the .update() prototype method.

Assuming I have a chart instance called myBar (the instance is what is returned from the Chart.js constructor), then I can use the below example to change the y-axes title.

myBar.options.scales.yAxes[0].scaleLabel.labelString = "My New Title";
myBar.update();

Here is a codepen that demonstrates a working example of this. Just click on the "Change Title" button to see if work.