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Getting Properties With Event Handlers

Page Summary

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 
  
 initMap 
 () 
  
 { 
  
 // Request needed libraries. 
  
 const 
  
 { 
  
 Map 
  
 } 
  
 = 
  
 await 
  
 google 
 . 
 maps 
 . 
 importLibrary 
 ( 
 "maps" 
 ) 
  
 as 
  
 google 
 . 
 maps 
 . 
 MapsLibrary 
 ; 
  
 const 
  
 mapElement 
  
 = 
  
 document 
 . 
 querySelector 
 ( 
 'gmp-map' 
 ) 
  
 as 
  
 google 
 . 
 maps 
 . 
 MapElement 
 ; 
  
 const 
  
 innerMap 
  
 = 
  
 mapElement 
 . 
 innerMap 
 ; 
  
 const 
  
 infowindow 
  
 = 
  
 new 
  
 google 
 . 
 maps 
 . 
 InfoWindow 
 ({ 
  
 content 
 : 
  
 "Change the zoom level" 
 , 
  
 position 
 : 
  
 mapElement.center 
 , 
  
 }); 
  
 infowindow 
 . 
 open 
 ( 
 innerMap 
 ); 
  
 innerMap 
 . 
 addListener 
 ( 
 "zoom_changed" 
 , 
  
 () 
  
 = 
>  
 { 
  
 infowindow 
 . 
 setContent 
 ( 
 "Zoom: " 
  
 + 
  
 innerMap 
 . 
 getZoom 
 () 
 ! 
 ); 
  
 }); 
 } 
 initMap 
 (); 
   index 
 . 
 ts

JavaScript

 async 
  
 function 
  
 initMap 
 () 
  
 { 
  
 // Request needed libraries. 
  
 const 
  
 { 
  
 Map 
  
 } 
  
 = 
  
 await 
  
 google 
 . 
 maps 
 . 
 importLibrary 
 ( 
 "maps" 
 ); 
  
 const 
  
 mapElement 
  
 = 
  
 document 
 . 
 querySelector 
 ( 
 'gmp-map' 
 ); 
  
 const 
  
 innerMap 
  
 = 
  
 mapElement 
 . 
 innerMap 
 ; 
  
 const 
  
 infowindow 
  
 = 
  
 new 
  
 google 
 . 
 maps 
 . 
 InfoWindow 
 ({ 
  
 content 
 : 
  
 "Change the zoom level" 
 , 
  
 position 
 : 
  
 mapElement 
 . 
 center 
 , 
  
 }); 
  
 infowindow 
 . 
 open 
 ( 
 innerMap 
 ); 
  
 innerMap 
 . 
 addListener 
 ( 
 "zoom_changed" 
 , 
  
 () 
  
 = 
>  
 { 
  
 infowindow 
 . 
 setContent 
 ( 
 "Zoom: " 
  
 + 
  
 innerMap 
 . 
 getZoom 
 ()); 
  
 }); 
 } 
 initMap 
 (); 
   index 
 . 
 js

CSS

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

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>
    <!-- prettier-ignore -->
    <script>(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: "AIzaSyA6myHzS10YXdcazAFalmXvDkrYCp5cLc8", v: "weekly" });</script>
  </head>

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

Try Sample

JSFiddle.net

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 
  
 https 
 : 
 //github.com/googlemaps-samples/js-api-samples.git 
 
  
  cd 
  
 samples 
 / 
 event 
 - 
 properties 
 
  
  npm 
  
 i 
 
  
  npm 
  
 start