Use a fallback image | UNL Map JS Docs

Use a coalesce expression to display another image when a requested image is not available.

Note

If you want to test this example, edit it in JSFiddle or CodePen and replace the "YOUR-OWN-API-KEY" and "YOUR-OWN-VPM-ID" placeholders with your actual api key and vpm id.

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>Use a fallback image</title>
<meta name="viewport" content="initial-scale=1,maximum-scale=1,user-scalable=no" />
<script src="https://unpkg.com/unl-map-js@0.1.5/lib/unl-map-js.js"></script>
<link href="https://unpkg.com/unl-map-js@0.1.5/lib/unl-map-js.css" rel="stylesheet" />
<link
href="https://unpkg.com/maplibre-gl@2.1.9/dist/maplibre-gl.css"
rel="stylesheet"
/>
<style>
	body { margin: 0; padding: 0; }
	#map { position: absolute; top: 0; bottom: 0; width: 100%; }
</style>
</head>
<body>
<div id="map"></div>
<script>
var map = new UnlSdk.Map({
container: "map",
apiKey: "YOUR-OWN-API-KEY",
vpmId: "YOUR-OWN-VPM-ID",
center: [-77, 38.75],
zoom: 5,
});
map.on("load", function () {
map.addSource("points", {
type: "geojson",
data: {
type: "FeatureCollection",
features: [
{
type: "Feature",
geometry: {
type: "Point",
coordinates: [-77.03238901390978, 38.913188059745586],
},
properties: {
title: "Washington DC",
icon: "monument",
},
},
{
type: "Feature",
geometry: {
type: "Point",
coordinates: [-79.9959, 40.4406],
},
properties: {
title: "Pittsburgh",
icon: "bridges",
},
},
{
type: "Feature",
geometry: {
type: "Point",
coordinates: [-76.2859, 36.8508],
},
properties: {
title: "Norfolk",
icon: "harbor",
},
},
],
},
});
map.addLayer({
id: "points",
type: "symbol",
source: "points",
layout: {
"icon-image": [
"coalesce",
["image", ["concat", ["get", "icon"], "-15"]],
["image", "marker_15"],
],
"text-field": ["get", "title"],
"text-font": ["Fira GO Regular"],
"text-offset": [0, 0.6],
"text-anchor": "top",
},
});
});
</script>
 
</body>
</html>