rectangle-event

Sample code supporting Google Maps Platform JavaScript API documentation. author(s): Geo Developer IX Documentation Team

HTML

<!doctype html>
<!--
@license
Copyright 2026 Google LLC. All Rights Reserved.
SPDX-License-Identifier: Apache-2.0
-->

<html>
  <head>
    <title>Listening to Events</title>

    <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))})({
            });
    </script>
  </head>
  <body>
    <gmp-map center="44.5452,-78.5389" zoom="9" map-id="DEMO_MAP_ID"></gmp-map>
  </body>
</html>

CSS

/**
 * @license
 * Copyright 2026 Google LLC. All Rights Reserved.
 * SPDX-License-Identifier: Apache-2.0
 */

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

JavaScript

'use strict';
/**
 * @license
 * Copyright 2026 Google LLC. All Rights Reserved.
 * SPDX-License-Identifier: Apache-2.0
 */

// This example adds a user-editable rectangle to the map.
// When the user changes the bounds of the rectangle,
// an info window pops up displaying the new bounds.

let rectangle;
let innerMap;

let infoWindow;

async function init() {
  const { Rectangle, InfoWindow } = await google.maps.importLibrary('maps');

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

  const bounds = {
    north: 44.599,
    south: 44.49,
    east: -78.443,
    west: -78.649,
  };

  // Define the rectangle and set its editable property to true.
  rectangle = new Rectangle({
    bounds,
    editable: true,
    draggable: true,
  });

  rectangle.setMap(innerMap);

  // Add an event listener on the rectangle.
  rectangle.addListener('bounds_changed', showNewRect);

  // Define an info window on the map.
  infoWindow = new InfoWindow();
}

/** Show the new coordinates for the rectangle in an info window. */
function showNewRect() {
  const ne = rectangle.getBounds().getNorthEast();
  const sw = rectangle.getBounds().getSouthWest();

  const contentString =
    '<b>Rectangle moved.</b><br>' +
    'New north-east corner: ' +
    ne.lat() +
    ', ' +
    ne.lng() +
    '<br>' +
    'New south-west corner: ' +
    sw.lat() +
    ', ' +
    sw.lng();

  // Set the info window's content and position.
  infoWindow.setContent(contentString);
  infoWindow.setPosition(ne);

  infoWindow.open(innerMap);
}

void init();