Data Layer: Event Handling
AI-generated Key Takeaways
This example demonstrates dynamically displaying information from a data layer when the mouse hovers over a KML feature object on a Google Map.
It uses GeoJSON data loaded onto the map and styled with custom colors and stroke weights.
A mouseover event listener is added to each feature, triggering the display of a specific property ("letter") in an info box.
The sample includes code in TypeScript and JavaScript, along with HTML and CSS for styling and structure.
This example uses a data layer to dynamically display information about aKML feature objectwhen under the mouse cursor.
Read thedocumentation.
TypeScript
letmap:google.maps.Map;functioninitMap():void{map=newgoogle.maps.Map(document.getElementById("map")asHTMLElement,{zoom:4,center:{lat:-28,lng:137},});// Load GeoJSON.map.data.loadGeoJson("https://storage.googleapis.com/maps-devrel/google.json");// Add some style.map.data.setStyle((feature)=>{return/** @type {google.maps.Data.StyleOptions} */{fillColor:feature.getProperty("color")asstring,strokeWeight:1,};});// Set mouseover event for each feature.map.data.addListener("mouseover",(event)=>{(document.getElementById("info-box")asHTMLElement).textContent=event.feature.getProperty("letter");});}declareglobal{interfaceWindow{initMap:()=>void;}}window.initMap=initMap;
JavaScript
letmap;functioninitMap(){map=newgoogle.maps.Map(document.getElementById("map"),{zoom:4,center:{lat:-28,lng:137},});// Load GeoJSON.map.data.loadGeoJson("https://storage.googleapis.com/maps-devrel/google.json",);// Add some style.map.data.setStyle((feature)=>{return/** @type {google.maps.Data.StyleOptions} */{fillColor:feature.getProperty("color"),strokeWeight:1,};});// Set mouseover event for each feature.map.data.addListener("mouseover",(event)=>{document.getElementById("info-box").textContent=event.feature.getProperty("letter");});}window.initMap=initMap;
CSS
/* * Always set the map height explicitly to define the size of the div element * that contains the map. */#map{height:100%;}/* * Optional: Makes the sample page fill the window. */html,body{height:100%;margin:0;padding:0;}#info-box{background-color:white;border:1pxsolidblack;bottom:30px;height:20px;padding:10px;position:absolute;left:30px;}
HTML
<html> <head> <title>Data Layer: Event Handling</title> <link rel="stylesheet" type="text/css" href="./style.css" /> <script type="module" src="./index.js"></script> </head> <body> <div></div> <div>?</div> <!-- The `defer` attribute causes the script to execute after the full HTML document has been parsed. For non-blocking uses, avoiding race conditions, and consistent behavior across browsers, consider loading using Promises. See https://developers.google.com/maps/documentation/javascript/load-maps-js-api for more information. --> <script src="https://maps.googleapis.com/maps/api/js?key=AIzaSyB41DRUbKWJHPxaFjMAwdrzWzbVKartNGg&callback=initMap&v=weekly" defer ></script> </body></html>
Try Sample
Clone Sample
Git and Node.js are required to run this sample locally. Follow theseinstructions to install Node.js and NPM. The following commands clone, install dependencies and start the sample application.
gitclone-bsample-layer-data-eventhttps://github.com/googlemaps/js-samples.gitcdjs-samplesnpminpmstart
Other samples can be tried by switching to any branch beginning withsample-SAMPLE_NAME.
gitcheckoutsample-SAMPLE_NAMEnpminpmstart
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Last updated 2025-11-21 UTC.