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Create and style clusters

Use MapLibre GL JS' built-in functions to visualize points as clusters.

<!DOCTYPE html>
<html lang="en">
<head>
    <title>Create and style clusters</title>
    <meta property="og:description" content="Use MapLibre GL JS' built-in functions to visualize points as clusters." />
    <meta charset='utf-8'>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel='stylesheet' href='https://unpkg.com/[email protected]/dist/maplibre-gl.css' />
    <script src='https://unpkg.com/[email protected]/dist/maplibre-gl.js'></script>
    <style>
        body { margin: 0; padding: 0; }
        html, body, #map { height: 100%; }
    </style>
</head>
<body>
<div id="map"></div>

<script>
    const map = new maplibregl.Map({
        container: 'map',
        style: 'https://api.maptiler.com/maps/streets/style.json?key=get_your_own_OpIi9ZULNHzrESv6T2vL',
        center: [-103.59179687498357, 40.66995747013945],
        zoom: 3
    });

    map.on('load', () => {
        // Add a new source from our GeoJSON data and
        // set the 'cluster' option to true. GL-JS will
        // add the point_count property to your source data.
        map.addSource('earthquakes', {
            type: 'geojson',
            // Point to GeoJSON data. This example visualizes all M1.0+ earthquakes
            // from 12/22/15 to 1/21/16 as logged by USGS' Earthquake hazards program.
            data: 'https://maplibre.org/maplibre-gl-js/docs/assets/earthquakes.geojson',
            cluster: true,
            clusterMaxZoom: 14, // Max zoom to cluster points on
            clusterRadius: 50 // Radius of each cluster when clustering points (defaults to 50)
        });

        map.addLayer({
            id: 'clusters',
            type: 'circle',
            source: 'earthquakes',
            filter: ['has', 'point_count'],
            paint: {
                // Use step expressions (https://maplibre.org/maplibre-style-spec/#expressions-step)
                // with three steps to implement three types of circles:
                //   * Blue, 20px circles when point count is less than 100
                //   * Yellow, 30px circles when point count is between 100 and 750
                //   * Pink, 40px circles when point count is greater than or equal to 750
                'circle-color': [
                    'step',
                    ['get', 'point_count'],
                    '#51bbd6',
                    100,
                    '#f1f075',
                    750,
                    '#f28cb1'
                ],
                'circle-radius': [
                    'step',
                    ['get', 'point_count'],
                    20,
                    100,
                    30,
                    750,
                    40
                ]
            }
        });

        map.addLayer({
            id: 'cluster-count',
            type: 'symbol',
            source: 'earthquakes',
            filter: ['has', 'point_count'],
            layout: {
                'text-field': '{point_count_abbreviated}',
                'text-font': ['DIN Offc Pro Medium', 'Arial Unicode MS Bold'],
                'text-size': 12
            }
        });

        map.addLayer({
            id: 'unclustered-point',
            type: 'circle',
            source: 'earthquakes',
            filter: ['!', ['has', 'point_count']],
            paint: {
                'circle-color': '#11b4da',
                'circle-radius': 4,
                'circle-stroke-width': 1,
                'circle-stroke-color': '#fff'
            }
        });

        // inspect a cluster on click
        map.on('click', 'clusters', async (e) => {
            const features = map.queryRenderedFeatures(e.point, {
                layers: ['clusters']
            });
            const clusterId = features[0].properties.cluster_id;
            const zoom = await map.getSource('earthquakes').getClusterExpansionZoom(clusterId);
            map.easeTo({
                center: features[0].geometry.coordinates,
                zoom
            });
        });

        // When a click event occurs on a feature in
        // the unclustered-point layer, open a popup at
        // the location of the feature, with
        // description HTML from its properties.
        map.on('click', 'unclustered-point', (e) => {
            const coordinates = e.features[0].geometry.coordinates.slice();
            const mag = e.features[0].properties.mag;
            let tsunami;

            if (e.features[0].properties.tsunami === 1) {
                tsunami = 'yes';
            } else {
                tsunami = 'no';
            }

            // Ensure that if the map is zoomed out such that
            // multiple copies of the feature are visible, the
            // popup appears over the copy being pointed to.
            while (Math.abs(e.lngLat.lng - coordinates[0]) > 180) {
                coordinates[0] += e.lngLat.lng > coordinates[0] ? 360 : -360;
            }

            new maplibregl.Popup()
                .setLngLat(coordinates)
                .setHTML(
                    `magnitude: ${mag}<br>Was there a tsunami?: ${tsunami}`
                )
                .addTo(map);
        });

        map.on('mouseenter', 'clusters', () => {
            map.getCanvas().style.cursor = 'pointer';
        });
        map.on('mouseleave', 'clusters', () => {
            map.getCanvas().style.cursor = '';
        });
    });
</script>
</body>
</html>