mapexample.dart

void main() {
  final mapOptions = new MapOptions()
    ..zoom = 15
    ..center = new LatLng(19.44059, -99.17000)
    ..mapTypeId = MapTypeId.ROADMAP;
  
  final map = new GMap(query("#map-canvas"), mapOptions);
  
  var circleOptions = new CircleOptions()
    ..strokeColor = "#006600" 
    ..strokeOpacity = 0.8
    ..strokeWeight = 2
    ..fillColor = "#D6FFD6"
    ..fillOpacity = 0.35
    ..map = map
    ..center = new LatLng(19.44059, -99.16524)
    ..radius= 1800;
  
  var circle = new Circle(circleOptions);
}

mapexample.js

function initialize() {
  var mapOptions = {
    zoom: 15,
    center: new google.maps.LatLng(19.44059, -99.17000),
    mapTypeId: google.maps.MapTypeId.ROADMAP
  };

  var circlecenter = new google.maps.LatLng(19.44059, -99.16524);

  var mapDiv = document.getElementById('map-canvas');
  var map = new google.maps.Map(mapDiv, mapOptions);

  var populationOptions = {
      strokeColor:  "#006600" ,
      strokeOpacity: 0.8,
      strokeWeight: 2,
      fillColor:  "#D6FFD6" ,
      fillOpacity: 0.35,
      map: map,
      center: circlecenter,
      radius: 1800
    };
   cityCircle = new google.maps.Circle(populationOptions);
}

function showAlert() {
  window.alert('DIV clicked');
}

google.maps.event.addDomListener(window, 'load', initialize);