Create and style features (4 of 4)

Add interactivity to your map by showing a city’s population count in a popup.

Prerequisites

Steps

Add mouse event handlers

1. Add a mouseenter event handler on the city-clusters layer. Change the cursor style to a pointer and ensure that the hovered feature is not a cluster.

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       map.on("mouseenter", "city-clusters", (e) => {
         map.getCanvas().style.cursor = "pointer";
         if (e.features[0].properties.cluster) return;
   
       });
   
   

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2. Create variables for the population value and feature coordinates. Format the POPULATION property for readability and extract the coordinates from geometry.coordinates.

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       map.on("mouseenter", "city-clusters", (e) => {
         map.getCanvas().style.cursor = "pointer";
         if (e.features[0].properties.cluster) return;
   
         const population = new Intl.NumberFormat().format(e.features[0].properties.POPULATION);
         const coordinates = e.features[0].geometry.coordinates.slice();
   
       });
   

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3. Add a mouseleave event handler on the city-clusters layer. Reset the cursor style back to default.

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       map.on("mouseleave", "city-clusters", () => {
         map.getCanvas().style.cursor = "";
   
       });
   

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Add a popup

1. Create a Popup() object.

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       const popup = new maplibregl.Popup({
         closeButton: false,
         closeOnClick: false
       });
   
       map.on("mouseenter", "city-clusters", (e) => {
         map.getCanvas().style.cursor = "pointer";
         if (e.features[0].properties.cluster) return;
   
         const population = new Intl.NumberFormat().format(e.features[0].properties.POPULATION);
         const coordinates = e.features[0].geometry.coordinates.slice();
   
       });
   
       map.on("mouseleave", "city-clusters", () => {
         map.getCanvas().style.cursor = "";
   
       });
   

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2. Inside the mouseenter event, set the popup's position using setLngLat, define the content to show the city's population count, and add it to the map.

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       const popup = new maplibregl.Popup({
         closeButton: false,
         closeOnClick: false
       });
   
       map.on("mouseenter", "city-clusters", (e) => {
         map.getCanvas().style.cursor = "pointer";
         if (e.features[0].properties.cluster) return;
   
         const population = new Intl.NumberFormat().format(e.features[0].properties.POPULATION);
         const coordinates = e.features[0].geometry.coordinates.slice();
   
         popup.setLngLat(coordinates).setHTML(`<b>Population</b>: ${population}`).addTo(map);
   
       });
   
       map.on("mouseleave", "city-clusters", () => {
         map.getCanvas().style.cursor = "";
   
       });
   

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3. Inside the mouseleave event, remove the popup from the map so it doesn’t stay visible after leaving the feature.

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       const popup = new maplibregl.Popup({
         closeButton: false,
         closeOnClick: false
       });
   
       map.on("mouseenter", "city-clusters", (e) => {
         map.getCanvas().style.cursor = "pointer";
         if (e.features[0].properties.cluster) return;
   
         const population = new Intl.NumberFormat().format(e.features[0].properties.POPULATION);
         const coordinates = e.features[0].geometry.coordinates.slice();
   
         popup.setLngLat(coordinates).setHTML(`<b>Population</b>: ${population}`).addTo(map);
   
       });
   
       map.on("mouseleave", "city-clusters", () => {
         map.getCanvas().style.cursor = "";
   
         popup.remove();
   
       });
   

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Run the app

Run the app.

When you hover over a city, a popup should appear with the city's population.

Congratulations!

You have completed the Create and style features how-to. The application displays clustered U.S. cities with populations over 250,000. It allows you to zoom in on a cluster and hover over it to see its population.

What's next?

To explore additional ArcGIS capabilities, go to Tutorials.