Mapbox GL JS getBounds()/fitBounds()

I'm using Mapbox GL JS v0.14.2 and I've searched high and low through the documentation and very little is clear about this.

If you use the standard JS API, it's very clear to 'fit map to markers' using an example they have provided (https://www.mapbox.com/mapbox.js/example/v1.0.0/fit-map-to-markers/); however the setup when using the GL api is quite different. The GL API has getBounds() (https://www.mapbox.com/mapbox-gl-js/api/#Map.getBounds) but because you don't have a named layer, like the standard JS API, so I'm struggling to work out how to use getBounds() at all.

I've found this (Mapbox GL JS API Set Bounds) but surely can't be the right answer?

This is the bulk of my setup; excluding JSON setup and other options.

mapboxgl.accessToken = '<myaccesstoken>';

var markers = <?php echo $programme_json; ?>;

var map = new mapboxgl.Map({
    container: 'map',
    style: 'mapbox://styles/richgc/cikyo5bse00nqb0lxebkfn2bm',
    center: [-1.470085, 53.381129],
    zoom: 15
});

map.on('style.load', function() {
    map.addSource('markers', {
        'type': 'geojson',
        'data': markers
    });

    map.addLayer({
        "id": "markers",
        "interactive": true,
        "type": "symbol",
        "source": "markers",
        "layout": {
            "icon-image": "venue-map-icon-blue",
            'icon-size': 0.5,
            "icon-allow-overlap": true
        }
    });

    map.scrollZoom.disable();

});

I have tried the following:

alert(map.getBounds()); // LngLatBounds(LngLat(-1.4855345239256508, 53.37642500812015), LngLat(-1.4546354760740883, 53.38583247227842))
var bounds = [[-1.4855345239256508, 53.37642500812015],[-1.4546354760740883, 53.38583247227842]]
map.fitBounds(bounds);

So I know how to fitBounds, but I'm unsure how to get them map.getBounds() just seems to return the set centre position lng/lat.

Markers JSON:

var markers = {"type":"FeatureCollection","features":[{"type":"Feature","properties":{"title":"Site Gallery","url":"\/Freelance\/art-sheffield-2016\/programme\/site-gallery\/","summary":"Duis arcu tortor, suscipit eget, imperdiet nec, imperdiet iaculis, ipsum. Donec id justo. Aenean tellus metus, bibendum sed, posuere ac, mattis non, nunc. Suspendisse feugiat. Etiam rhoncus.","image":"\/Freelance\/art-sheffield-2016\/site\/assets\/files\/1032\/site_gallery.jpg","marker-symbol":"venue-map-icon-blue","colour":"blue"},"geometry":{"type":"Point","coordinates":["-1.466439","53.376842"]}},{"type":"Feature","properties":{"title":"Moore Street Substation","url":"\/Freelance\/art-sheffield-2016\/programme\/moore-street-substation\/","summary":"","image":null,"marker-symbol":"venue-map-icon-green","colour":"green"},"geometry":{"type":"Point","coordinates":["-1.477881","53.374798"]}},{"type":"Feature","properties":{"title":"S1 Artspace","url":"\/Freelance\/art-sheffield-2016\/programme\/s1-artspace\/","summary":"","image":null,"marker-symbol":"venue-map-icon-red","colour":"red"},"geometry":{"type":"Point","coordinates":["-1.459620","53.380562"]}}]};

Solution 1:

If you want to fit map to markers, you can create bounds that contains all markers.

var bounds = new mapboxgl.LngLatBounds();

markers.features.forEach(function(feature) {
    bounds.extend(feature.geometry.coordinates);
});

map.fitBounds(bounds);

Solution 2:

For a solution that will work for all GeoJSON objects, not just a set of markers, check out Mapbox's Turf.js.

This code was very helpful to me: https://bl.ocks.org/danswick/83a8ddff7fb9193176a975a02a896792

But just to repeat the basics in case that link dies:

var bounds = turf.bbox(markers);
map.fitBounds(bounds, {padding: 20});

The extent method mentioned in the linked code has been deprecated in favour of bbox, but the result is the same.

Solution 3:

Mapbox's own geojson-extent plugin will do the trick. Assuming your markers object is valid GeoJSON, you can simply pass it to the geojsonExtent() function to get a set of bounds that you can then pass to fitBounds().

Once you load the geojson-extent.js file (e.g., by using a <script> tag in your HTML code), you should be able to do this to fit your map to the bounds of your GeoJSON markers object:

map.fitBounds(geojsonExtent(markers));

UPDATE

GeoJSONLint reports that your markers object is not valid GeoJSON because the elements in each position are being interpreted as strings, not numbers. If you remove the quotes from the lon-lat coordinates, it should work fine:

var markers = {
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {
        "title": "Site Gallery",
        "url": "\/Freelance\/art-sheffield-2016\/programme\/site-gallery\/",
        "summary": "Duis arcu tortor, suscipit eget, imperdiet nec, imperdiet iaculis, ipsum. Donec id justo. Aenean tellus metus, bibendum sed, posuere ac, mattis non, nunc. Suspendisse feugiat. Etiam rhoncus.",
        "image": "\/Freelance\/art-sheffield-2016\/site\/assets\/files\/1032\/site_gallery.jpg",
        "marker-symbol": "venue-map-icon-blue",
        "colour": "blue"
      },
      "geometry": {
        "type": "Point",
        "coordinates": [
          -1.466439,
          53.376842
        ]
      }
    },
    {
      "type": "Feature",
      "properties": {
        "title": "Moore Street Substation",
        "url": "\/Freelance\/art-sheffield-2016\/programme\/moore-street-substation\/",
        "summary": "",
        "image": null,
        "marker-symbol": "venue-map-icon-green",
        "colour": "green"
      },
      "geometry": {
        "type": "Point",
        "coordinates": [
          -1.477881,
          53.374798
        ]
      }
    },
    {
      "type": "Feature",
      "properties": {
        "title": "S1 Artspace",
        "url": "\/Freelance\/art-sheffield-2016\/programme\/s1-artspace\/",
        "summary": "",
        "image": null,
        "marker-symbol": "venue-map-icon-red",
        "colour": "red"
      },
      "geometry": {
        "type": "Point",
        "coordinates": [
          -1.459620,
          53.380562
        ]
      }
    }
  ]
};

Solution 4:

This is my solution based on the reduce operation from a Mapbox example.

It works for geojson that contain point features and multi-point features like lines.

let bounds = geoJSON.features.reduce(function(bounds, feature) {
  if(!Array.isArray(feature.geometry.coordinates[0])) { // point feature
    return bounds.extend(feature.geometry.coordinates);
  } else {
    return feature.geometry.coordinates.reduce(function(bounds, coord) {
      return bounds.extend(coord);
    }, bounds);
  }
}, new mapboxgl.LngLatBounds());

map.fitBounds(bounds, {
  maxZoom: 12,
  padding: 30, // in px, to make markers on the top edge visible
})