Update a feature in realtime

Change an existing feature on your map in realtime by updating its data

<!DOCTYPE html>
    <meta charset='utf-8' />
    <title>Update a feature in realtime</title>
    <meta name='viewport' content='initial-scale=1,maximum-scale=1,user-scalable=no' />
    <script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.52.0/mapbox-gl.js'></script>
    <link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.52.0/mapbox-gl.css' rel='stylesheet' />
        body { margin:0; padding:0; }
        #map { position:absolute; top:0; bottom:0; width:100%; }

<div id='map'></div>

<script src='//d3js.org/d3.v3.min.js' charset='utf-8'></script>
mapboxgl.accessToken = '<your access token here>';
var map = new mapboxgl.Map({
    container: 'map',
    style: 'mapbox://styles/mapbox/satellite-v9',
    zoom: 0

map.on('load', function () {
    // We use D3 to fetch the JSON here so that we can parse and use it separately
    // from GL JS's use in the added source. You can use any request method (library
    // or otherwise) that you want.
    d3.json('https://docs.mapbox.com/mapbox-gl-js/assets/hike.geojson', function(err, data) {
        if (err) throw err;

        // save full coordinate list for later
        var coordinates = data.features[0].geometry.coordinates;

        // start by showing just the first coordinate
        data.features[0].geometry.coordinates = [coordinates[0]];

        // add it to the map
        map.addSource('trace', { type: 'geojson', data: data });
            "id": "trace",
            "type": "line",
            "source": "trace",
            "paint": {
                "line-color": "yellow",
                "line-opacity": 0.75,
                "line-width": 5

        // setup the viewport
        map.jumpTo({ 'center': coordinates[0], 'zoom': 14 });

        // on a regular basis, add more coordinates from the saved list and update the map
        var i = 0;
        var timer = window.setInterval(function() {
            if (i < coordinates.length) {
            } else {
        }, 10);

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