Create a Hover Effect

Highlight a feature when the user hovers over it using feature state.

const API_KEY = 'toursprung';

    const map = new maptoolkit.Map({
        container: 'map',
        style: `https://static.maptoolkit.net/styles/toursprung/terrain.json?api_key=${API_KEY}`,
        center: [-100.486052, 37.830348],
        zoom: 2,
        attributionControl: { compact: false }
    });

    map.addControl(new maptoolkit.NavigationControl(), 'top-right');

    let hoveredStateId = null;

    map.on('load', () => {
        map.addSource('states', {
            type: 'geojson',
            data: 'https://maplibre.org/maplibre-gl-js/docs/assets/us_states.geojson'
        });

        map.addLayer({
            id: 'state-fills',
            type: 'fill',
            source: 'states',
            paint: {
                'fill-color': '#627BC1',
                'fill-opacity': [
                    'case',
                    ['boolean', ['feature-state', 'hover'], false],
                    1,
                    0.5
                ]
            }
        });

        map.addLayer({
            id: 'state-borders',
            type: 'line',
            source: 'states',
            paint: {
                'line-color': '#627BC1',
                'line-width': 2
            }
        });

        map.on('mousemove', 'state-fills', (e) => {
            if (e.features.length > 0) {
                if (hoveredStateId !== null) {
                    map.setFeatureState({ source: 'states', id: hoveredStateId }, { hover: false });
                }
                hoveredStateId = e.features[0].id;
                map.setFeatureState({ source: 'states', id: hoveredStateId }, { hover: true });
            }
        });

        map.on('mouseleave', 'state-fills', () => {
            if (hoveredStateId !== null) {
                map.setFeatureState({ source: 'states', id: hoveredStateId }, { hover: false });
            }
            hoveredStateId = null;
        });
    });

<!DOCTYPE html>
<html lang="en">
<head>
    <title>Create a Hover Effect – Maptoolkit Maps JS</title>
    <meta property="og:description" content="Highlight a feature when the user hovers over it using feature state." />
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <script src="https://unpkg.com/@maptoolkit/maps@11.0.0-beta.2/dist/maptoolkit.js"></script>
    <link rel="stylesheet" href="https://unpkg.com/@maptoolkit/maps@11.0.0-beta.2/dist/maptoolkit.css" />
    <style>
        html, body { width: 100%; height: 100%; margin: 0; padding: 0; }
        #map { width: 100%; height: 100%; }
    </style>
</head>
<body>
<div id="map"></div>
<script>
    const API_KEY = 'toursprung';

    const map = new maptoolkit.Map({
        container: 'map',
        style: `https://static.maptoolkit.net/styles/toursprung/terrain.json?api_key=${API_KEY}`,
        center: [-100.486052, 37.830348],
        zoom: 2,
        attributionControl: { compact: false }
    });

    map.addControl(new maptoolkit.NavigationControl(), 'top-right');

    let hoveredStateId = null;

    map.on('load', () => {
        map.addSource('states', {
            type: 'geojson',
            data: 'https://maplibre.org/maplibre-gl-js/docs/assets/us_states.geojson'
        });

        map.addLayer({
            id: 'state-fills',
            type: 'fill',
            source: 'states',
            paint: {
                'fill-color': '#627BC1',
                'fill-opacity': [
                    'case',
                    ['boolean', ['feature-state', 'hover'], false],
                    1,
                    0.5
                ]
            }
        });

        map.addLayer({
            id: 'state-borders',
            type: 'line',
            source: 'states',
            paint: {
                'line-color': '#627BC1',
                'line-width': 2
            }
        });

        map.on('mousemove', 'state-fills', (e) => {
            if (e.features.length > 0) {
                if (hoveredStateId !== null) {
                    map.setFeatureState({ source: 'states', id: hoveredStateId }, { hover: false });
                }
                hoveredStateId = e.features[0].id;
                map.setFeatureState({ source: 'states', id: hoveredStateId }, { hover: true });
            }
        });

        map.on('mouseleave', 'state-fills', () => {
            if (hoveredStateId !== null) {
                map.setFeatureState({ source: 'states', id: hoveredStateId }, { hover: false });
            }
            hoveredStateId = null;
        });
    });
</script>
</body>
</html>

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