Create a Gradient Dashed Line Using an Expression

Create a dashed line with a gradient color along its length.

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: [-77.035, 38.875],
        zoom: 12,
        attributionControl: { compact: false }
    });

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

    const geojson = {
        type: 'FeatureCollection',
        features: [{
            type: 'Feature',
            properties: {},
            geometry: {
                type: 'LineString',
                coordinates: [
                    [-77.044211, 38.852924],
                    [-77.045659, 38.860158],
                    [-77.044232, 38.862326],
                    [-77.040879, 38.865454],
                    [-77.039936, 38.867698],
                    [-77.040338, 38.86943],
                    [-77.04264,  38.872528],
                    [-77.03696,  38.878424],
                    [-77.032309, 38.87937],
                    [-77.030056, 38.880945],
                    [-77.027645, 38.881779],
                    [-77.026946, 38.882645],
                    [-77.026942, 38.885502],
                    [-77.028054, 38.887449],
                    [-77.02806,  38.892088],
                    [-77.03364,  38.892108],
                    [-77.033643, 38.899926]
                ]
            }
        }]
    };

    map.on('load', () => {
        map.addSource('line', {
            type: 'geojson',
            lineMetrics: true,
            data: geojson
        });

        map.addLayer({
            id: 'line',
            type: 'line',
            source: 'line',
            paint: {
                'line-color': 'red',
                'line-width': 14,
                'line-gradient': [
                    'interpolate', ['linear'], ['line-progress'],
                    0,   'blue',
                    0.1, 'royalblue',
                    0.3, 'cyan',
                    0.5, 'lime',
                    0.7, 'yellow',
                    1,   'red'
                ],
                'line-dasharray': [10, 2.4]
            },
            layout: {
                'line-cap': 'round',
                'line-join': 'round'
            }
        });
    });

<!DOCTYPE html>
<html lang="en">
<head>
    <title>Create a Gradient Dashed Line Using an Expression – Maptoolkit Maps JS</title>
    <meta property="og:description" content="Create a dashed line with a gradient color along its length." />
    <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: [-77.035, 38.875],
        zoom: 12,
        attributionControl: { compact: false }
    });

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

    const geojson = {
        type: 'FeatureCollection',
        features: [{
            type: 'Feature',
            properties: {},
            geometry: {
                type: 'LineString',
                coordinates: [
                    [-77.044211, 38.852924],
                    [-77.045659, 38.860158],
                    [-77.044232, 38.862326],
                    [-77.040879, 38.865454],
                    [-77.039936, 38.867698],
                    [-77.040338, 38.86943],
                    [-77.04264,  38.872528],
                    [-77.03696,  38.878424],
                    [-77.032309, 38.87937],
                    [-77.030056, 38.880945],
                    [-77.027645, 38.881779],
                    [-77.026946, 38.882645],
                    [-77.026942, 38.885502],
                    [-77.028054, 38.887449],
                    [-77.02806,  38.892088],
                    [-77.03364,  38.892108],
                    [-77.033643, 38.899926]
                ]
            }
        }]
    };

    map.on('load', () => {
        map.addSource('line', {
            type: 'geojson',
            lineMetrics: true,
            data: geojson
        });

        map.addLayer({
            id: 'line',
            type: 'line',
            source: 'line',
            paint: {
                'line-color': 'red',
                'line-width': 14,
                'line-gradient': [
                    'interpolate', ['linear'], ['line-progress'],
                    0,   'blue',
                    0.1, 'royalblue',
                    0.3, 'cyan',
                    0.5, 'lime',
                    0.7, 'yellow',
                    1,   'red'
                ],
                'line-dasharray': [10, 2.4]
            },
            layout: {
                'line-cap': 'round',
                'line-join': 'round'
            }
        });
    });
</script>
</body>
</html>

Create a Draggable Point Create a Gradient Line Using an Expression