const chart = Highcharts.chart('container', {
    chart: {
        type: 'scatter'
    },
    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 random = 0.5; // for first, automated test

document.getElementById('button').addEventListener('click', () => {
    chart.series[0].addPoint([
        (random || Math.random()) * 12,
        (random || Math.random()) * 200
    ]);
    random = null;
});
