Getting Properties With Event Handlers

  • This example demonstrates how to listen for the zoom_changed event on a Google Map.

  • When the zoom level changes, an info window updates to display the current zoom level.

  • The sample code uses the Google Maps JavaScript API and is provided in both TypeScript and JavaScript.

  • Users can interact with a live demo via JSFiddle or Google Cloud Shell, and the code can be cloned for local execution.

This example listens for the zoom_changed event and updates an info window when the zoom level changes.

Read the documentation.

TypeScript

async function init() {
    // Request needed libraries.
    const { InfoWindow } = await google.maps.importLibrary('maps');

    const mapElement = document.querySelector('gmp-map')!;
    const innerMap = mapElement.innerMap;

    const infoWindow = new InfoWindow({
        content: 'Change the zoom level',
        position: mapElement.center,
    });

    infoWindow.open(innerMap);

    innerMap.addListener('zoom_changed', () => {
        infoWindow.setContent('Zoom: ' + innerMap.getZoom()!);
    });
}

void init();

JavaScript

async function init() {
    // Request needed libraries.
    const { InfoWindow } = await google.maps.importLibrary('maps');

    const mapElement = document.querySelector('gmp-map');
    const innerMap = mapElement.innerMap;

    const infoWindow = new InfoWindow({
        content: 'Change the zoom level',
        position: mapElement.center,
    });

    infoWindow.open(innerMap);

    innerMap.addListener('zoom_changed', () => {
        infoWindow.setContent('Zoom: ' + innerMap.getZoom());
    });
}

void init();

CSS

/* 
 * Optional: Makes the sample page fill the window. 
 */
html,
body {
    height: 100%;
    margin: 0;
    padding: 0;
}

HTML

<html>
    <head>
        <title>Getting Properties With Event Handlers</title>

        <link rel="stylesheet" type="text/css" href="./style.css" />
        <script type="module" src="./index.js"></script>
        <script>
            // prettier-ignore
            (g=>{var h,a,k,p="The Google Maps JavaScript API",c="google",l="importLibrary",q="__ib__",m=document,b=window;b=b[c]||(b[c]={});var d=b.maps||(b.maps={}),r=new Set,e=new URLSearchParams,u=()=>h||(h=new Promise(async(f,n)=>{await (a=m.createElement("script"));e.set("libraries",[...r]+"");for(k in g)e.set(k.replace(/[A-Z]/g,t=>"_"+t[0].toLowerCase()),g[k]);e.set("callback",c+".maps."+q);a.src=`https://maps.${c}apis.com/maps/api/js?`+e;d[q]=f;a.onerror=()=>h=n(Error(p+" could not load."));a.nonce=m.querySelector("script[nonce]")?.nonce||"";m.head.append(a)}));d[l]?console.warn(p+" only loads once. Ignoring:",g):d[l]=(f,...n)=>r.add(f)&&u().then(()=>d[l](f,...n))})({
                key: "GOOGLE_MAPS_API_KEY" 
            });
        </script>
    </head>

    <body>
        <gmp-map
            center="-25.363882,131.044922"
            zoom="4"
            map-id="DEMO_MAP_ID"></gmp-map>
    </body>
</html>

Clone Sample

Git and Node.js are required to run this sample locally. Follow these instructions to install Node.js and NPM. You will also need a Google Maps API key.

The following commands clone the repository, install dependencies, and copy the environment file. 

  git clone https://github.com/googlemaps-samples/js-api-samples.git
  cd js-api-samples
  npm i
  cp .env.template .env

Once you copy the environment file, make sure to open the .env file and replace <Insert your own development API key here> with your actual API key before starting the sample. 

  cd samples/event-properties
  npm start