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>

        <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="41.85, -87.65" zoom="12">
            <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 setCenterButton = document.getElementById('btnCenterMap');
    const resetCenterButton = document.getElementById('btnSetCenter');

    // Set up the click event listener for the 'Center Map' button. Set the map
    // to the currently stored center.
    setCenterButton.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.
    resetCenterButton.addEventListener('click', () => {
        const newCenter = innerMap.getCenter();

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

void init();