// 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;Note: Read the guide on using TypeScript and Google Maps. 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;Note: The JavaScript is compiled from the TypeScript snippet. 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;
}
HTML
<html>
<head>
<title>Circles</title>
<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 script 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>
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