Style a boundary polygon

  • This example highlights the boundary polygon of a single region on a map using the Maps JavaScript API.

  • It utilizes the FeatureLayer to style the boundary with a purple fill and border for a specific place ID (Hana, HI).

  • The sample code is provided in TypeScript and JavaScript, allowing developers to choose their preferred language.

  • Users can explore the sample through JSFiddle, Google Cloud Shell, or by cloning the repository and running it locally.

This example map demonstrates highlighting the boundary polygon for a single region.

Read the documentation.

TypeScript

let featureLayer: google.maps.FeatureLayer;

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;

    // Get the feature layer.
    featureLayer = innerMap.getFeatureLayer('LOCALITY');

    // Define a style with purple fill and border.
    const featureStyleOptions: google.maps.FeatureStyleOptions = {
        strokeColor: '#810FCB',
        strokeOpacity: 1.0,
        strokeWeight: 3.0,
        fillColor: '#810FCB',
        fillOpacity: 0.5,
    };

    // Apply the style to a single boundary.
    featureLayer.style = (options: google.maps.FeatureStyleFunctionOptions) => {
        const feature = options.feature as google.maps.PlaceFeature;
        if (feature.placeId === 'ChIJ0zQtYiWsVHkRk8lRoB1RNPo') {
            // Hana, HI
            return featureStyleOptions;
        }
        return null;
    };
}

void init();

JavaScript

let featureLayer;

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;

    // Get the feature layer.
    featureLayer = innerMap.getFeatureLayer('LOCALITY');

    // Define a style with purple fill and border.
    const featureStyleOptions = {
        strokeColor: '#810FCB',
        strokeOpacity: 1.0,
        strokeWeight: 3.0,
        fillColor: '#810FCB',
        fillOpacity: 0.5,
    };

    // Apply the style to a single boundary.
    featureLayer.style = (options) => {
        const feature = options.feature;
        if (feature.placeId === 'ChIJ0zQtYiWsVHkRk8lRoB1RNPo') {
            // Hana, HI
            return featureStyleOptions;
        }
        return null;
    };
}

void init();

CSS

/* 
 * 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;
}

HTML

<html>
    <head>
        <title>Boundaries Simple</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="20.773,-156.01"
            zoom="12"
            map-id="8b37d7206ccf0121d4414bb0"></gmp-map>
    </body>
</html>

Clone Sample

Git and Node.js are required to run this sample locally. Follow these instructions to install Node.js and NPM. You will also need a Google Maps API key.

The following commands clone the repository, install dependencies, and copy the environment file. 

  git clone https://github.com/googlemaps-samples/js-api-samples.git
  cd js-api-samples
  npm i
  cp .env.template .env

Once you copy the environment file, make sure to open the .env file and replace <Insert your own development API key here> with your actual API key before starting the sample. 

  cd samples/boundaries-simple
  npm start