control-custom-state

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>Adding State to Controls</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="41.85, -87.65" zoom="12" map-id="DEMO_MAP_ID">
      <div class="custom-control" slot="control-block-start-inline-center">
        <input
          type="button"
          class="button"
          id="btnCenterMap"
          value="Center Map"
          title="Click to recenter the map." />
        <input
          type="button"
          class="button"
          id="btnSetCenter"
          value="Set Center"
          title="Click to change the center of the map." />
      </div>
    </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;
}

#btnCenterMap,
#btnSetCenter {
  background-color: #fff;
  border: 2px solid #fff;
  border-radius: 3px;
  box-shadow: 0 2px 6px rgba(0, 0, 0, 0.3);
  cursor: pointer;
  float: left;
  margin-bottom: 22px;
  margin-top: 5px;
  text-align: center;
  color: rgb(25, 25, 25);
  font-family: Roboto, Arial, sans-serif;
  font-size: 15px;
  line-height: 25px;
}

#btnSetCenter {
  margin-left: 12px;
}

JavaScript

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

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

let center = {
  lat: 41.85,
  lng: -87.65,
};

async function init() {
  await google.maps.importLibrary('maps');

  innerMap = mapElement.innerMap;

  // Get the button UI elements.
  const centerMapButton = document.getElementById('btnCenterMap');
  const setCenterButton = document.getElementById('btnSetCenter');

  // Set up the click event listener for the 'Center Map' button. Set the map
  // to the currently stored center.
  centerMapButton.addEventListener('click', () => {
    const currentCenter = center;
    innerMap.setCenter(currentCenter);
  });

  // Set up the click event listener for 'Set Center': Set the center of
  // the control to the current center of the map.
  setCenterButton.addEventListener('click', () => {
    const newCenter = innerMap.getCenter();

    if (newCenter) {
      center = newCenter;
    }
  });
}

void init();