Display a popup

Learn how to display feature attributes in a popup.

A popup, also known as a "popup", is a visual element that displays information about a feature when it is clicked. You typically style and configure a popup using HTML and CSS for each layer in a map. popups can display attribute values, calculated values, or rich content such as images, charts, or videos.

In this tutorial, you create an interactive popup for the Trailheads vector tile layer in the Santa Monica Mountains. When a feature is clicked, a popup is displayed containing the name of the trail and the service that manages it.

Prerequisites

Steps

Create a new pen

1. To get started, either complete the Display a map tutorial or use this pen.

Set the API key

To access location services, you need an API key or OAuth 2.0 access token. To learn how to create and scope your key, visit the Create an API key tutorial.

1. Go to your dashboard to get an API key. The API key must be scoped to access the services used in this tutorial.

2. In CodePen, update apiKey to use your key.

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   const apiKey = "YOUR_API_KEY";
   const basemapEnum = "arcgis/streets";
   const map = new maplibregl.Map({
     container: "map", // the id of the div element
     style: `https://basemapstyles-api.arcgis.com/arcgis/rest/services/styles/v2/styles/${basemapEnum}?token=${apiKey}`,
     zoom: 12, // starting zoom
     center: [-118.805, 34.027] // starting location [longitude, latitude]
   });
   

Add a load handler

You need to wait for the map to be completely loaded before adding any layers

1. Add an event handler to the map load event.

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       <script>
         const apiKey = "YOUR_API_KEY";
         const basemapEnum = "arcgis/streets";
         const map = new maplibregl.Map({
           container: "map", // the id of the div element
           style: `https://basemapstyles-api.arcgis.com/arcgis/rest/services/styles/v2/styles/${basemapEnum}?token=${apiKey}`,
           zoom: 12, // starting zoom
           center: [-118.805, 34.027] // starting location [longitude, latitude]
         });
   
         map.once("load", () => {
   
         });
   
       </script>
   

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Add the trailheads layer

You will use a vector tile source and a circle layer to display the trailheads.

1. Inside the load handler, add a source called trailheads and set the url property of the vector tile layer.

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         map.once("load", () => {
   
           map.addSource("trailheads", {
             type: "vector",
             tiles: [
               "https://vectortileservices3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trailheads/VectorTileServer/tile/{z}/{y}/{x}.pbf"
             ]
           });
   
         });
   

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2. Add a circle layer called trailheads-circle, which references the trailheads source.

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         map.once("load", () => {
   
           map.addSource("trailheads", {
             type: "vector",
             tiles: [
               "https://vectortileservices3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/Trailheads/VectorTileServer/tile/{z}/{y}/{x}.pbf"
             ]
           });
   
           map.addLayer({
             id: "trailheads-circle",
             type: "circle",
             source: "trailheads",
             "source-layer": "Trailheads",
   
             paint: {
               "circle-color": "hsla(200,80%,70%,0.5)",
               "circle-stroke-width": 2,
               "circle-radius": 5,
               "circle-stroke-color": "hsl(200,80%,50%)"
             }
           });
   
         });
   

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Add a click handler

To display a popup appear when a trailheads feature is clicked, add a click event handler. This handler is called with the features under the pointer where you clicked.

1. Add a handler for theclick event on the Map. Pass the trailheads-circle id to the on method so the handler is only called when you click on that layer. Inside, store the first element of the features property to a trailhead variable.

   More info

   If there are multiple overlapping features where you click, all of those features will be included in the features array. The first element listed will be the topmost feature.

   See the MapLibre GL JS documentation for more map events you can respond to.

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             paint: {
               "circle-color": "hsla(200,80%,70%,0.5)",
               "circle-stroke-width": 2,
               "circle-radius": 5,
               "circle-stroke-color": "hsl(200,80%,50%)"
             }
           });
   
           map.on("click", "trailheads-circle", (e) => {
             const trailhead = e.features[0];
   
           });
   

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Create the popup

You create a new Popup with mapboxgl.Popup. The default parameters give a simple white bubble which stays open until you click its close button or somewhere on the map.

To add content, you use Popup.setHTML. Use your trailhead variable to make the HTML string. It is a GeoJSON object, so the clicked trailhead's attributes are in a properties object. The name of the trail is stored in TRL_NAME and the name of the park service is in PARK_NAME.

1. Create a new Popup.

   More info

   You can pass additional options, to change behavior such as whether there is a close button in the corner. See the MapLibre documentation for more details.

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           map.on("click", "trailheads-circle", (e) => {
             const trailhead = e.features[0];
   
             new maplibregl.Popup()
   
           });
   

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2. Use Popup.setHTML to set the contents: the name of the trail in an <h3> tag, then the name of the park service.

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             new maplibregl.Popup()
   
               .setHTML(`<b>${trailhead.properties.TRL_NAME}</b>${trailhead.properties.PARK_NAME}`)
   
   

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Add the popup to the map

When you create the Popup, it is not immediately added to the map. You need to call setLngLat to provide the position, then addTo to attach it to the Map.

1. Set the location of the Popup to the location of the feature clicked on by using the setLngLat method, then add it to the map.

   More info

   Most methods of Popup return the Popup itself. This means you can chain method calls, using each output to call the next.

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             new maplibregl.Popup()
   
               .setHTML(`<b>${trailhead.properties.TRL_NAME}</b>${trailhead.properties.PARK_NAME}`)
   
               .setLngLat(trailhead.geometry.coordinates)
               .addTo(map);
   

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Change the cursor on hover

To indicate that you can interact with a layer by clicking, it is useful to change the mouse cursor to a pointing hand when hovering over the layer. You use Map.getCanvas to access the map's <canvas> element, so you can set the CSS cursor property.

1. Add a handler to the mouseenter event, changing the cursor to a pointer.

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           map.on("click", "trailheads-circle", (e) => {
             const trailhead = e.features[0];
   
             new maplibregl.Popup()
   
               .setHTML(`<b>${trailhead.properties.TRL_NAME}</b>${trailhead.properties.PARK_NAME}`)
   
               .setLngLat(trailhead.geometry.coordinates)
               .addTo(map);
   
           });
   
           map.on("mouseenter", "trailheads-circle", () => {
             map.getCanvas().style.cursor = "pointer";
           });
   
   

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2. Add a handler to the mouseleave event, changing the cursor back to the default.

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           map.on("mouseenter", "trailheads-circle", () => {
             map.getCanvas().style.cursor = "pointer";
           });
   
           map.on("mouseleave", "trailheads-circle", () => {
             map.getCanvas().style.cursor = "";
           });
   

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Run the app

In CodePen, run your code to display the map.

The map view should display the Trailheads feature layer. When you hover over a feature the cursor should change. When you click a feature, the name of the trailhead and its park name is displayed in a popup.

What's next?

Learn how to use additional ArcGIS location services in these tutorials: