boundaries-choropleth

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

HTML

<!doctype html>
<!--
 @license
 Copyright 2025 Google LLC. All Rights Reserved.
 SPDX-License-Identifier: Apache-2.0
-->

<html>
  <head>
    <title>Choropleth Map</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="40.76,-101.64"
      zoom="5"
      map-id="8b37d7206ccf01219cd548d3"></gmp-map>
  </body>
</html>

CSS

/**
 * @license
 * Copyright 2025 Google LLC. All Rights Reserved.
 * SPDX-License-Identifier: Apache-2.0
 */

/* 
 * Always set the map height explicitly to define the size of the div element
 * that contains the map. 
 */
gmp-map {
  height: 100%;
}

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

JavaScript

'use strict';
/**
 * @license
 * Copyright 2025 Google LLC. All Rights Reserved.
 * SPDX-License-Identifier: Apache-2.0
 */

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

  // Get the gmp-map element.
  const mapElement = document.querySelector('gmp-map');

  // Get the inner map.
  const innerMap = mapElement.innerMap;

  const featureLayer = innerMap.getFeatureLayer('ADMINISTRATIVE_AREA_LEVEL_1');

  featureLayer.style = (featureStyleFunctionOptions) => {
    const placeFeature = featureStyleFunctionOptions.feature;
    const population = states[placeFeature.placeId];

    let fillColor;
    // Specify colors using any of the following:
    // * Named ('green')
    // * Hexadecimal ('#FF0000')
    // * RGB ('rgb(0, 0, 255)')
    // * HSL ('hsl(60, 100%, 50%)')

    if (population < 2000000) {
      fillColor = 'green';
    } else if (population < 5000000) {
      fillColor = 'red';
    } else if (population < 10000000) {
      fillColor = 'blue';
    } else if (population < 40000000) {
      fillColor = 'yellow';
    }
    return {
      fillColor,
      fillOpacity: 0.5,
    };
  };

  // Population data by state.
  const states = {
    ChIJdf5LHzR_hogR6czIUzU0VV4: 5039877, // Alabama
    ChIJG8CuwJzfAFQRNduKqSde27w: 732673, // Alaska
    'ChIJaxhMy-sIK4cRcc3Bf7EnOUI': 7276316, // Arizona
    'ChIJYSc_dD-e0ocR0NLf_z5pBaQ': 3025891, // Arkansas
    ChIJPV4oX_65j4ARVW8IJ6IJUYs: 39237836, // California
    ChIJt1YYm3QUQIcR_6eQSTGDVMc: 5812069, // Colorado
    ChIJpVER8hFT5okR5XBhBVttmq4: 3605597, // Connecticut
    ChIJO9YMTXYFx4kReOgEjBItHZQ: 1003384, // Delaware
    ChIJvypWkWV2wYgR0E7HW9MTLvc: 21781128, // Florida
    ChIJV4FfHcU28YgR5xBP7BC8hGY: 10799566, // Georgia
    ChIJBeB5Twbb_3sRKIbMdNKCd0s: 1441553, // Hawaii
    ChIJ6Znkhaj_WFMRWIf3FQUwa9A: 1900923, // Idaho
    ChIJGSZubzgtC4gRVlkRZFCCFX8: 12671469, // Illinois
    ChIJHRv42bxQa4gRcuwyy84vEH4: 6805985, // Indiana
    ChIJGWD48W9e7ocR2VnHV0pj78Y:...