Filter symbols using a dynamic expression
This examples demonstrates a technique for filtering symbols on a map when the user toggles a checkbox.
This technique creates a symbol layer whose source includes several features with different icon properties. Expressions are used for filtering the layer to only show features whose icon property matches the selected checkboxes.
When a checkbox is toggled, setFilter is called to apply a dynamic filter expression based on the current state of the checkboxes.
An alternative technique using a multiple layers and setLayoutProperty to toggle their visibility is available at Filter symbols by toggling a checkbox
Referencing images in a style's sprite
This example uses the Mapbox Light style. The icon-image used in this example comes from the Mapbox Light style's sprite.
To view all available images in a style's sprite or add additional images, open the style in Mapbox Studio and click the Images tab. To add a new image to the style at runtime see the Add an icon to the map example.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Filter symbols using a dynamic expression</title>
<meta name="viewport" content="initial-scale=1,maximum-scale=1,user-scalable=no">
<link href="https://api.mapbox.com/mapbox-gl-js/v3.8.0/mapbox-gl.css" rel="stylesheet">
<script src="https://api.mapbox.com/mapbox-gl-js/v3.8.0/mapbox-gl.js"></script>
<style>
body { margin: 0; padding: 0; }
#map { position: absolute; top: 0; bottom: 0; width: 100%; }
</style>
</head>
<body>
<style>
.filter-group {
font:
12px/20px 'Helvetica Neue',
Arial,
Helvetica,
sans-serif;
font-weight: 600;
position: absolute;
top: 10px;
right: 10px;
z-index: 1;
border-radius: 3px;
width: 120px;
color: #fff;
}
.filter-group input[type='checkbox']:first-child + label {
border-radius: 3px 3px 0 0;
}
.filter-group label:last-child {
border-radius: 0 0 3px 3px;
border: none;
}
.filter-group input[type='checkbox'] {
display: none;
}
.filter-group input[type='checkbox'] + label {
background-color: #3386c0;
display: block;
cursor: pointer;
padding: 10px;
border-bottom: 1px solid rgba(0, 0, 0, 0.25);
}
.filter-group input[type='checkbox'] + label {
background-color: #3386c0;
text-transform: capitalize;
}
.filter-group input[type='checkbox'] + label:hover,
.filter-group input[type='checkbox']:checked + label {
background-color: #4ea0da;
}
.filter-group input[type='checkbox']:checked + label:before {
content: '✔';
margin-right: 5px;
}
</style>
<div id="map"></div>
<nav id="filter-group" class="filter-group"></nav>
<script>
// TO MAKE THE MAP APPEAR YOU MUST
// ADD YOUR ACCESS TOKEN FROM
// https://account.mapbox.com
mapboxgl.accessToken = 'YOUR_MAPBOX_ACCESS_TOKEN';
// This GeoJSON contains features that include an "icon"
// property. The value of the "icon" property corresponds
// to an image in the Mapbox Light style's sprite. (Note:
// the name of images is the value of the "icon" property
// + "-15".)
const places = {
'type': 'FeatureCollection',
'features': [
{
'type': 'Feature',
'properties': {
'icon': 'theatre'
},
'geometry': {
'type': 'Point',
'coordinates': [-77.038659, 38.931567]
}
},
{
'type': 'Feature',
'properties': {
'icon': 'theatre'
},
'geometry': {
'type': 'Point',
'coordinates': [-77.003168, 38.894651]
}
},
{
'type': 'Feature',
'properties': {
'icon': 'bar'
},
'geometry': {
'type': 'Point',
'coordinates': [-77.090372, 38.881189]
}
},
{
'type': 'Feature',
'properties': {
'icon': 'bicycle'
},
'geometry': {
'type': 'Point',
'coordinates': [-77.052477, 38.943951]
}
},
{
'type': 'Feature',
'properties': {
'icon': 'music'
},
'geometry': {
'type': 'Point',
'coordinates': [-77.031706, 38.914581]
}
},
{
'type': 'Feature',
'properties': {
'icon': 'music'
},
'geometry': {
'type': 'Point',
'coordinates': [-77.020945, 38.878241]
}
},
{
'type': 'Feature',
'properties': {
'icon': 'music'
},
'geometry': {
'type': 'Point',
'coordinates': [-77.007481, 38.876516]
}
}
]
};
const filterGroup = document.getElementById('filter-group');
const map = new mapboxgl.Map({
container: 'map',
// Choose from Mapbox's core styles, or make your own style with Mapbox Studio
style: 'mapbox://styles/mapbox/light-v11',
center: [-77.04, 38.907],
zoom: 11.15
});
map.on('load', () => {
// Add a GeoJSON source containing place coordinates and information.
map.addSource('places', {
'type': 'geojson',
'data': places
});
// Add a symbol layer showing all features in the source
map.addLayer({
'id': 'symbol-places',
'type': 'symbol',
'source': 'places',
'layout': {
// These icons are a part of the Mapbox Light style.
// To view all images available in a Mapbox style, open
// the style in Mapbox Studio and click the "Images" tab.
// To add a new image to the style at runtime see
// https://docs.mapbox.com/mapbox-gl-js/example/add-image/
'icon-image': ['get', 'icon'],
'icon-allow-overlap': true
}
});
// this function will be called whenever a checkbox is toggled
const updateLayerFilter = () => {
// get an array of icon names that corresponds to the currently checked checkboxes
const checkedSymbols = [...document.getElementsByTagName('input')]
.filter((el) => el.checked)
.map((el) => el.id);
// use an 'in' expression to filter the layer
map.setFilter('symbol-places', ['in', 'icon', ...checkedSymbols]);
};
// get an array of all unique `icon` properties
const symbols = [];
for (const feature of places.features) {
const symbol = feature.properties.icon;
if (!symbols.includes(symbol)) symbols.push(symbol);
}
// for each `icon` value, create a checkbox and label
for (const symbol of symbols) {
const input = document.createElement('input');
input.type = 'checkbox';
input.id = symbol;
input.checked = true;
filterGroup.appendChild(input);
const label = document.createElement('label');
label.setAttribute('for', symbol);
label.textContent = symbol;
filterGroup.appendChild(label);
// When any checkbox changes, update the filter.
input.addEventListener('change', updateLayerFilter);
}
});
</script>
</body>
</html>
This code snippet will not work as expected until you replace
YOUR_MAPBOX_ACCESS_TOKEN with an access token from your Mapbox account.Was this example helpful?