Data Layer: Event Handling

This example uses a data layer to dynamically display information about a KML feature object when under the mouse cursor.

Read the documentation.

TypeScript

let map: google.maps.Map;

function initMap(): void {
  map = new google.maps.Map(document.getElementById("map") as HTMLElement, {
    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") as string,
      strokeWeight: 1,
    };
  });

  // Set mouseover event for each feature.
  map.data.addListener("mouseover", (event) => {
    (document.getElementById("info-box") as HTMLElement).textContent =
      event.feature.getProperty("letter");
  });
}

declare global {
  interface Window {
    initMap: () => void;
  }
}
window.initMap = initMap;
index.ts

JavaScript

let map;

function initMap() {
  map = new google.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;
index.js

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: 1px solid black;
  bottom: 30px;
  height: 20px;
  padding: 10px;
  position: absolute;
  left: 30px;
}

style.css

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 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>
index.html

Try Sample

Clone Sample

Git and Node.js are required to run this sample locally. Follow these instructions to install Node.js and NPM. The following commands clone, install dependencies and start the sample application. 

  git clone -b sample-layer-data-event https://github.com/googlemaps/js-samples.git
  cd js-samples
  npm i
  npm start

Other samples can be tried by switching to any branch beginning with sample-SAMPLE_NAME. 

  git checkout sample-SAMPLE_NAME
  npm i
  npm start