Spline updating each second

author(s): Torstein Hønsi

HTML

<script src="https://code.highcharts.com/highcharts.js"></script>
<script src="https://code.highcharts.com/modules/exporting.js"></script>
<script src="https://code.highcharts.com/modules/export-data.js"></script>
<script src="https://code.highcharts.com/modules/accessibility.js"></script>

<figure class="highcharts-figure">
    <div id="container"></div>
    <p class="highcharts-description">
        Chart showing data updating every second, with old data being removed.
    </p>
</figure>

CSS

body {
    font-family:
        -apple-system,
        BlinkMacSystemFont,
        "Segoe UI",
        Roboto,
        Helvetica,
        Arial,
        "Apple Color Emoji",
        "Segoe UI Emoji",
        "Segoe UI Symbol",
        sans-serif;
    background: var(--highcharts-background-color);
    color: var(--highcharts-neutral-color-100);
}

.highcharts-figure,
.highcharts-data-table table {
    min-width: 320px;
    max-width: 800px;
    margin: 1em auto;
}

#container {
    height: 400px;
}

.highcharts-data-table table {
    font-family: Verdana, sans-serif;
    border-collapse: collapse;
    border: 1px solid var(--highcharts-neutral-color-10, #e6e6e6);
    margin: 10px auto;
    text-align: center;
    width: 100%;
    max-width: 500px;
}

.highcharts-data-table caption {
    padding: 1em 0;
    font-size: 1.2em;
    color: var(--highcharts-neutral-color-60, #666);
}

.highcharts-data-table th {
    font-weight: 600;
    padding: 0.5em;
}

.highcharts-data-table td,
.highcharts-data-table th,
.highcharts-data-table caption {
    padding: 0.5em;
}

.highcharts-data-table thead tr,
.highcharts-data-table tbody tr:nth-child(even) {
    background: var(--highcharts-neutral-color-3, #f7f7f7);
}

.highcharts-description {
    background: light-dark(#f2f6f2, #323232);
    border-radius: 0 4px 4px 0;
    border-left: 2px solid light-dark(#1d6aff, #fff);
    font-size: 0.8rem;
    font-style: italic;
    padding: 8px 16px;
    margin: 2em 10px 1em;
}

TypeScript

// On chart load, start an interval that adds points to the chart and animate
// the pulsating marker.
const onChartLoad = function (this: Highcharts.Chart): void {
    setInterval(() => {
        const x = (new Date()).getTime(), // current time
            y = Math.random();

        this.series[0].addPoint([x, y], true, true);
    }, 1000);
};

// Create the initial data
const data: Highcharts.PointOptionsObject[] = (function () {
    const data = [];
    const time = new Date().getTime();

    for (let i = -19; i <= 0; i += 1) {
        data.push({
            x: time + i * 1000,
            y: Math.random()
        });
    }
    return data;
}());

// Plugin to add a pulsating marker on add point
(({ addEvent, Series }) => {
    const pulseMap = new WeakMap<Highcharts.Series, Highcharts.SVGElement>();
    addEvent(Series, 'addPoint', (
        e: Highcharts.SeriesAddPointEventObject
    ) => {
        const series = e.target,
            options = series.options as Highcharts.SeriesScatterOptions,
            x = e.point.x;

        let pulse = pulseMap.get(series);
        pulse ||= series.chart.renderer.circle()
            .add(series.markerGroup);
        pulseMap.set(series, pulse);

        setTimeout(() => {
            pulse
                .attr({
                    r: options.marker.radius,
                    opacity: 1,
                    fill: series.color
                })
                .animate({
                    r: 20,
                    opacity: 0
                }, {
                    duration: 1000,
                    step: () => {
                        const point = series.points[series.points.length - 1],
                            graphic = point?.graphic;
                        if (point && point.x === x && graphic) {
                            pulse.attr({
                                x: Number(graphic.attr('x')) +
                                    Number(graphic.attr('width')) / 2,
                              ...