How to chose one feature from multifeature GeoJSON

[Michael Johansson]

Hi!

I have an external GeoJSON file with a couple of polygon features. You can see it here http://bl.ocks.org/d/41b25d26989d211bd86744dd4ffb82f2
I'm sorry if this has been asked before but I didn't find a good answer.

I want to add one polygon feature from that GeoJSON to my leaflet map, not all the features. How would I go about doing that?.

As of now this is how my script looks like. Not that much at the moment since I don't really know where to start. So any pointers in a direction would be appreciated.

<script>
    var map = L.map('map').setView([43.64701, -79.39425], 15);

    //Load Geojson from external, local file
    $.getJSON("polygons.geojson",function(data){
    // add GeoJSON layer to the map once the file is loaded
    geojsonLayer = L.geoJson(data).addTo(map);
    map.fitBounds(geojsonLayer.getBounds());
    });

</script>

The end goal is to add one polygon at a time. Then extract coordinates from that polygon and then calling an API with those coordinates to get a image from that area. Then simply add that as a layer to leaflet.
I know how to do it all, except for the load only one polygon at a time from the GeoJSON.

//Michael

[Matt Travis]

Hi Michael

You could try using the filter function: http://leafletjs.com/reference-1.0.2.html#geojson-filter

Example here: http://gis.stackexchange.com/questions/189988/filtering-geojson-data-to-include-in-leaflet-map

Not sure if that works with mapbox though which is what your example is using.

Cheers

Matt

[Michael Johansson]

Thank you!
I did solve it with the filter function.
I don't know how I missed that method :)

And I am using leaflet, the link was just to an online service to show GeoJSON stuff.

The code for the map part looks like this now:

    var map = L.map('map')

        .addLayer(OSMlayer)
        .setView([42.444508, -76.499491], 12);
   
    //Load the GeoJSON
    var promise = $.getJSON("polygons.geojson");
    promise.then(function(data) {
               
        //A variable for all the polygons
        var allpolygons = L.geoJson(data);
               
        //A variable for only one polygon selected from the "ID" property in the GeoJSON
        var firstpoly = L.geoJson(data, {
            filter: function(feature, layer) {
                return feature.properties.ID == 1;
            }
        });
        // Add the first feature to the map
        firstpoly.addTo(map)
});