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;
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;
/** 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>
<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 id="map"></div>
<div id="info-box">?</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>
Git and Node.js are required to run this sample locally. Follow theseinstructionsto install Node.js and NPM. The following commands clone, install dependencies and start the sample application.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-09-04 UTC."],[[["\u003cp\u003eThis example demonstrates dynamically displaying information from a data layer when the mouse hovers over a KML feature object on a Google Map.\u003c/p\u003e\n"],["\u003cp\u003eIt uses GeoJSON data loaded onto the map and styled with custom colors and stroke weights.\u003c/p\u003e\n"],["\u003cp\u003eA mouseover event listener is added to each feature, triggering the display of a specific property ("letter") in an info box.\u003c/p\u003e\n"],["\u003cp\u003eThe sample includes code in TypeScript and JavaScript, along with HTML and CSS for styling and structure.\u003c/p\u003e\n"]]],["This code dynamically displays KML feature information on a Google Map using a data layer. It initializes a map, loads GeoJSON data, and styles features based on their \"color\" property. A mouseover event listener is added to each feature, updating an \"info-box\" element with the feature's \"letter\" property when the cursor is over it. CSS styles the map and info box. HTML structures the page with the map and info box elements and load the Javascript and the google maps API.\n"],null,["This example uses a data layer to dynamically display information about a\n[KML feature object](/maps/documentation/javascript/kmllayer#kml_feature_details)\nwhen under the mouse cursor.\n\nRead the\n[documentation](/maps/documentation/javascript/datalayer#add_event_handlers). \n\nTypeScript \n\n```typescript\nlet map: google.maps.Map;\n\nfunction initMap(): void {\n map = new google.maps.Map(document.getElementById(\"map\") as HTMLElement, {\n zoom: 4,\n center: { lat: -28, lng: 137 },\n });\n\n // Load GeoJSON.\n map.data.loadGeoJson(\n \"https://storage.googleapis.com/maps-devrel/google.json\"\n );\n\n // Add some style.\n map.data.setStyle((feature) =\u003e {\n return /** @type {google.maps.Data.StyleOptions} */ {\n fillColor: feature.getProperty(\"color\") as string,\n strokeWeight: 1,\n };\n });\n\n // Set mouseover event for each feature.\n map.data.addListener(\"mouseover\", (event) =\u003e {\n (document.getElementById(\"info-box\") as HTMLElement).textContent =\n event.feature.getProperty(\"letter\");\n });\n}\n\ndeclare global {\n interface Window {\n initMap: () =\u003e void;\n }\n}\nwindow.initMap = initMap;https://github.com/googlemaps/js-samples/blob/2683f7366fb27829401945d2a7e27d77ed2df8e5/samples/layer-data-event/index.ts#L8-L43\n```\n| **Note:** Read the [guide](/maps/documentation/javascript/using-typescript) on using TypeScript and Google Maps.\n\nJavaScript \n\n```javascript\nlet map;\n\nfunction initMap() {\n map = new google.maps.Map(document.getElementById(\"map\"), {\n zoom: 4,\n center: { lat: -28, lng: 137 },\n });\n // Load GeoJSON.\n map.data.loadGeoJson(\n \"https://storage.googleapis.com/maps-devrel/google.json\",\n );\n // Add some style.\n map.data.setStyle((feature) =\u003e {\n return /** @type {google.maps.Data.StyleOptions} */ {\n fillColor: feature.getProperty(\"color\"),\n strokeWeight: 1,\n };\n });\n // Set mouseover event for each feature.\n map.data.addListener(\"mouseover\", (event) =\u003e {\n document.getElementById(\"info-box\").textContent =\n event.feature.getProperty(\"letter\");\n });\n}\n\nwindow.initMap = initMap;https://github.com/googlemaps/js-samples/blob/2683f7366fb27829401945d2a7e27d77ed2df8e5/dist/samples/layer-data-event/docs/index.js#L7-L34\n```\n| **Note:** The JavaScript is compiled from the TypeScript snippet.\n\nCSS \n\n```css\n/* \n * Always set the map height explicitly to define the size of the div element\n * that contains the map. \n */\n#map {\n height: 100%;\n}\n\n/* \n * Optional: Makes the sample page fill the window. \n */\nhtml,\nbody {\n height: 100%;\n margin: 0;\n padding: 0;\n}\n\n#info-box {\n background-color: white;\n border: 1px solid black;\n bottom: 30px;\n height: 20px;\n padding: 10px;\n position: absolute;\n left: 30px;\n}\nhttps://github.com/googlemaps/js-samples/blob/2683f7366fb27829401945d2a7e27d77ed2df8e5/dist/samples/layer-data-event/docs/style.css#L7-L34\n```\n\nHTML \n\n```html\n\u003chtml\u003e\n \u003chead\u003e\n \u003ctitle\u003eData Layer: Event Handling\u003c/title\u003e\n\n \u003clink rel=\"stylesheet\" type=\"text/css\" href=\"./style.css\" /\u003e\n \u003cscript type=\"module\" src=\"./index.js\"\u003e\u003c/script\u003e\n \u003c/head\u003e\n \u003cbody\u003e\n \u003cdiv id=\"map\"\u003e\u003c/div\u003e\n \u003cdiv id=\"info-box\"\u003e?\u003c/div\u003e\n\n \u003c!-- \n The `defer` attribute causes the script to execute after the full HTML\n document has been parsed. For non-blocking uses, avoiding race conditions,\n and consistent behavior across browsers, consider loading using Promises. See\n https://developers.google.com/maps/documentation/javascript/load-maps-js-api\n for more information.\n --\u003e\n \u003cscript\n src=\"https://maps.googleapis.com/maps/api/js?key=AIzaSyB41DRUbKWJHPxaFjMAwdrzWzbVKartNGg&callback=initMap&v=weekly\"\n defer\n \u003e\u003c/script\u003e\n \u003c/body\u003e\n\u003c/html\u003ehttps://github.com/googlemaps/js-samples/blob/2683f7366fb27829401945d2a7e27d77ed2df8e5/dist/samples/layer-data-event/docs/index.html#L8-L31\n```\n\nTry Sample \n[JSFiddle.net](https://jsfiddle.net/gh/get/library/pure/googlemaps/js-samples/tree/master/dist/samples/layer-data-event/jsfiddle) [Google Cloud Shell](https://ssh.cloud.google.com/cloudshell/editor?cloudshell_git_repo=https%3A%2F%2Fgithub.com%2Fgooglemaps%2Fjs-samples&cloudshell_git_branch=sample-layer-data-event&cloudshell_tutorial=cloud_shell_instructions.md&cloudshell_workspace=.)\n\nClone Sample\n\n\nGit and Node.js are required to run this sample locally. Follow these [instructions](https://docs.npmjs.com/downloading-and-installing-node-js-and-npm) to install Node.js and NPM. The following commands clone, install dependencies and start the sample application. \n\n git clone -b sample-layer-data-event https://github.com/googlemaps/js-samples.git\n cd js-samples\n npm i\n npm start\n\n\nOther samples can be tried by switching to any branch beginning with `sample-`\u003cvar translate=\"no\"\u003eSAMPLE_NAME\u003c/var\u003e. \n\n git checkout sample-\u003cvar translate=\"no\"\u003e\u003cspan class=\"devsite-syntax-nx\"\u003eSAMPLE_NAME\u003c/span\u003e\u003c/var\u003e\n npm i\n npm start"]]
