const chart = Highcharts.chart('container', {
    subtitle: {
        text: 'Subtitle'
    },
    xAxis: {
        categories: ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']
    },
    series: [{
        data: [29.9, 71.5, 106.4, 129.2, 144.0, 176.0, 135.6, 148.5, 216.4, 194.1, 95.6, 54.4]
    }]
});

let i = 0;

document.getElementById('title').addEventListener('click', () => {
    chart.title.update({ text: 'New title ' + i });
    i += 1;
});

document.getElementById('subtitle').addEventListener('click', () => {
    chart.subtitle.update({ text: 'New title ' + i });
    i += 1;
});

document.getElementById('color').addEventListener('click', () => {
    chart.title.update({
        style: {
            color: 'red'
        }
    });
    chart.subtitle.update({
        style: {
            color: 'green'
        }
    });
});
