Fit to the bounds of a LineString | Mapbox GL JS

Get the bounds of a LineString by passing its first coordinates to LngLatBounds and chaining extend to include the last coordinates.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Fit to the bounds of a LineString</title>
<meta name="viewport" content="initial-scale=1,maximum-scale=1,user-scalable=no">
<link href="https://api.mapbox.com/mapbox-gl-js/v3.3.0/mapbox-gl.css" rel="stylesheet">
<script src="https://api.mapbox.com/mapbox-gl-js/v3.3.0/mapbox-gl.js"></script>
<style>
body { margin: 0; padding: 0; }
#map { position: absolute; top: 0; bottom: 0; width: 100%; }
</style>
</head>
<body>
<style>
    .btn-control {
        font:
            bold 12px/20px 'Helvetica Neue',
            Arial,
            Helvetica,
            sans-serif;
        background-color: #3386c0;
        color: #fff;
        position: absolute;
        top: 20px;
        left: 50%;
        z-index: 1;
        border: none;
        width: 200px;
        margin-left: -100px;
        display: block;
        cursor: pointer;
        padding: 10px 20px;
        border-radius: 3px;
    }

    .btn-control:hover {
        background-color: #4ea0da;
    }
</style>
<div id="map"></div>
<button id="zoomto" class="btn-control">Zoom to bounds</button>

<script>
	// TO MAKE THE MAP APPEAR YOU MUST
	// ADD YOUR ACCESS TOKEN FROM
	// https://account.mapbox.com
	mapboxgl.accessToken = 'YOUR_MAPBOX_ACCESS_TOKEN';
    // A GeoJSON object with a LineString route from the White House to Capitol Hill
    const geojson = {
        'type': 'FeatureCollection',
        'features': [
            {
                'type': 'Feature',
                'geometry': {
                    'type': 'LineString',
                    'coordinates': [
                        [-77.0366048812866, 38.89873175227713],
                        [-77.03364372253417, 38.89876515143842],
                        [-77.03364372253417, 38.89549195896866],
                        [-77.02982425689697, 38.89549195896866],
                        [-77.02400922775269, 38.89387200688839],
                        [-77.01519012451172, 38.891416957534204],
                        [-77.01521158218382, 38.892068305429156],
                        [-77.00813055038452, 38.892051604275686],
                        [-77.00832366943358, 38.89143365883688],
                        [-77.00818419456482, 38.89082405874451],
                        [-77.00815200805664, 38.88989712255097]
                    ]
                },
                'properties': {},
            }
        ]
    };

    const map = new mapboxgl.Map({
        container: 'map',
        // Choose from Mapbox's core styles, or make your own style with Mapbox Studio
        style: 'mapbox://styles/mapbox/light-v11',
        center: [-77.0214, 38.897],
        zoom: 12
    });

    map.on('load', () => {
        map.addSource('LineString', {
            'type': 'geojson',
            'data': geojson
        });
        map.addLayer({
            'id': 'LineString',
            'type': 'line',
            'source': 'LineString',
            'layout': {
                'line-join': 'round',
                'line-cap': 'round'
            },
            'paint': {
                'line-color': '#BF93E4',
                'line-width': 5
            }
        });

        document.getElementById('zoomto').addEventListener('click', () => {
            // Geographic coordinates of the LineString
            const coordinates = geojson.features[0].geometry.coordinates;

            // Create a 'LngLatBounds' with both corners at the first coordinate.
            const bounds = new mapboxgl.LngLatBounds(
                coordinates[0],
                coordinates[0]
            );

            // Extend the 'LngLatBounds' to include every coordinate in the bounds result.
            for (const coord of coordinates) {
                bounds.extend(coord);
            }

            map.fitBounds(bounds, {
                padding: 20
            });
        });
    });
</script>

</body>
</html>
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