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Filter symbols by toggling a list

Filter a set of symbols based on a property value in the data.

<!DOCTYPE html>
<html lang="en">
<head>
    <title>Filter symbols by toggling a list</title>
    <meta property="og:description" content="Filter a set of symbols based on a property value in the data." />
    <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>
<style>
    .filter-group {
        font: 12px/20px 'Helvetica Neue', Arial, Helvetica, sans-serif;
        font-weight: 600;
        position: absolute;
        top: 10px;
        right: 10px;
        z-index: 1;
        border-radius: 3px;
        width: 120px;
        color: #fff;
    }

    .filter-group input[type='checkbox']:first-child + label {
        border-radius: 3px 3px 0 0;
    }

    .filter-group label:last-child {
        border-radius: 0 0 3px 3px;
        border: none;
    }

    .filter-group input[type='checkbox'] {
        display: none;
    }

    .filter-group input[type='checkbox'] + label {
        background-color: #3386c0;
        display: block;
        cursor: pointer;
        padding: 10px;
        border-bottom: 1px solid rgba(0, 0, 0, 0.25);
    }

    .filter-group input[type='checkbox'] + label {
        background-color: #3386c0;
        text-transform: capitalize;
    }

    .filter-group input[type='checkbox'] + label:hover,
    .filter-group input[type='checkbox']:checked + label {
        background-color: #4ea0da;
    }

    .filter-group input[type='checkbox']:checked + label:before {
        content: '✔';
        margin-right: 5px;
    }
</style>
<div id="map"></div>
<nav id="filter-group" class="filter-group"></nav>

<script>
    const places = {
        'type': 'FeatureCollection',
        'features': [
            {
                'type': 'Feature',
                'properties': {
                    'icon': 'theatre'
                },
                'geometry': {
                    'type': 'Point',
                    'coordinates': [-77.038659, 38.931567]
                }
            },
            {
                'type': 'Feature',
                'properties': {
                    'icon': 'theatre'
                },
                'geometry': {
                    'type': 'Point',
                    'coordinates': [-77.003168, 38.894651]
                }
            },
            {
                'type': 'Feature',
                'properties': {
                    'icon': 'bar'
                },
                'geometry': {
                    'type': 'Point',
                    'coordinates': [-77.090372, 38.881189]
                }
            },
            {
                'type': 'Feature',
                'properties': {
                    'icon': 'bicycle'
                },
                'geometry': {
                    'type': 'Point',
                    'coordinates': [-77.052477, 38.943951]
                }
            },
            {
                'type': 'Feature',
                'properties': {
                    'icon': 'music'
                },
                'geometry': {
                    'type': 'Point',
                    'coordinates': [-77.031706, 38.914581]
                }
            },
            {
                'type': 'Feature',
                'properties': {
                    'icon': 'music'
                },
                'geometry': {
                    'type': 'Point',
                    'coordinates': [-77.020945, 38.878241]
                }
            },
            {
                'type': 'Feature',
                'properties': {
                    'icon': 'music'
                },
                'geometry': {
                    'type': 'Point',
                    'coordinates': [-77.007481, 38.876516]
                }
            }
        ]
    };

    const filterGroup = document.getElementById('filter-group');
    const map = new maplibregl.Map({
        container: 'map',
        style:
            'https://api.maptiler.com/maps/streets/style.json?key=get_your_own_OpIi9ZULNHzrESv6T2vL',
        center: [-77.04, 38.907],
        zoom: 11.15
    });

    map.on('load', () => {
        // Add a GeoJSON source containing place coordinates and information.
        map.addSource('places', {
            'type': 'geojson',
            'data': places
        });

        places.features.forEach((feature) => {
            const symbol = feature.properties['icon'];
            const layerID = `poi-${symbol}`;

            // Add a layer for this symbol type if it hasn't been added already.
            if (!map.getLayer(layerID)) {
                map.addLayer({
                    'id': layerID,
                    'type': 'symbol',
                    'source': 'places',
                    'layout': {
                        'icon-image': `${symbol}_15`,
                        'icon-overlap': 'always'
                    },
                    'filter': ['==', 'icon', symbol]
                });

                // Add checkbox and label elements for the layer.
                const input = document.createElement('input');
                input.type = 'checkbox';
                input.id = layerID;
                input.checked = true;
                filterGroup.appendChild(input);

                const label = document.createElement('label');
                label.setAttribute('for', layerID);
                label.textContent = symbol;
                filterGroup.appendChild(label);

                // When the checkbox changes, update the visibility of the layer.
                input.addEventListener('change', (e) => {
                    map.setLayoutProperty(
                        layerID,
                        'visibility',
                        e.target.checked ? 'visible' : 'none'
                    );
                });
            }
        });
    });
</script>
</body>
</html>