Circles

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This example creates circles on the map, representing populations in North America.

Read the documentation.

TypeScript

// This example creates circles on the map, representing populations in North
// America.

// First, create an object containing LatLng and population for each city.

interface City {
  center: google.maps.LatLngLiteral;
  population: number;
}

const citymap: Record<string, City> = {
  chicago: {
    center: { lat: 41.878, lng: -87.629 },
    population: 2714856,
  },
  newyork: {
    center: { lat: 40.714, lng: -74.005 },
    population: 8405837,
  },
  losangeles: {
    center: { lat: 34.052, lng: -118.243 },
    population: 3857799,
  },
  vancouver: {
    center: { lat: 49.25, lng: -123.1 },
    population: 603502,
  },
};

function initMap(): void {
  // Create the map.
  const map = new google.maps.Map(
    document.getElementById("map") as HTMLElement,
    {
      zoom: 4,
      center: { lat: 37.09, lng: -95.712 },
      mapTypeId: "terrain",
    }
  );

  // Construct the circle for each value in citymap.
  // Note: We scale the area of the circle based on the population.
  for (const city in citymap) {
    // Add the circle for this city to the map.
    const cityCircle = new google.maps.Circle({
      strokeColor: "#FF0000",
      strokeOpacity: 0.8,
      strokeWeight: 2,
      fillColor: "#FF0000",
      fillOpacity: 0.35,
      map,
      center: citymap[city].center,
      radius: Math.sqrt(citymap[city].population) * 100,
    });
  }
}

declare global {
  interface Window {
    initMap: () => void;
  }
}
window.initMap = initMap;
index.ts

JavaScript

const citymap = {
  chicago: {
    center: { lat: 41.878, lng: -87.629 },
    population: 2714856,
  },
  newyork: {
    center: { lat: 40.714, lng: -74.005 },
    population: 8405837,
  },
  losangeles: {
    center: { lat: 34.052, lng: -118.243 },
    population: 3857799,
  },
  vancouver: {
    center: { lat: 49.25, lng: -123.1 },
    population: 603502,
  },
};

function initMap() {
  // Create the map.
  const map = new google.maps.Map(document.getElementById("map"), {
    zoom: 4,
    center: { lat: 37.09, lng: -95.712 },
    mapTypeId: "terrain",
  });

  // Construct the circle for each value in citymap.
  // Note: We scale the area of the circle based on the population.
  for (const city in citymap) {
    // Add the circle for this city to the map.
    const cityCircle = new google.maps.Circle({
      strokeColor: "#FF0000",
      strokeOpacity: 0.8,
      strokeWeight: 2,
      fillColor: "#FF0000",
      fillOpacity: 0.35,
      map,
      center: citymap[city].center,
      radius: Math.sqrt(citymap[city].population) * 100,
    });
  }
}

window.initMap = initMap;
index.js

CSS

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

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

style.css

HTML

<html>
  <head>
    <title>Circles</title>
    <script src="https://polyfill.io/v3/polyfill.min.js?features=default"></script>

    <link rel="stylesheet" type="text/css" href="./style.css" />
    <script type="module" src="./index.js"></script>
  </head>
  <body>
    <div id="map"></div>

    <!-- 
      The `defer` attribute causes the callback to execute after the full HTML
      document has been parsed. For non-blocking uses, avoiding race conditions,
      and consistent behavior across browsers, consider loading using Promises.
      See https://developers.google.com/maps/documentation/javascript/load-maps-js-api
      for more information.
      -->
    <script
      src="https://maps.googleapis.com/maps/api/js?key=AIzaSyB41DRUbKWJHPxaFjMAwdrzWzbVKartNGg&callback=initMap&v=weekly"
      defer
    ></script>
  </body>
</html>
index.html

Try Sample

Clone Sample

Git and Node.js are required to run this sample locally. Follow these instructions to install Node.js and NPM. The following commands clone, install dependencies and start the sample application. 

  git clone -b sample-circle-simple https://github.com/googlemaps/js-samples.git
  cd js-samples
  npm i
  npm start

Other samples can be tried by switching to any branch beginning with sample-SAMPLE_NAME. 

  git checkout sample-SAMPLE_NAME
  npm i
  npm start