Circles

HTML

<div id="map"></div>
<script src="https://maps.googleapis.com/maps/api/js?key=AIzaSyBIwzALxUPNbatRBj3Xi1Uhp0fFzwWNBkE&callback=initMap&libraries=&v=weekly" async></script>

CSS

#map {
  height: 100%;
}

html,
body {
  height: 100%;
  margin: 0;
  padding: 0;
}

JavaScript

const cities = [{
    "lat": 40.7127837,
    "lng": -74.0059413,
    "city": "New York"
  },
  {
    "lat": 34.0522342,
    "lng": -118.2436849,
    "city": "Los Angeles"
  },
  {
    "lat": 41.8781136,
    "lng": -87.6297982,
    "city": "Chicago"
  },
  {
    "lat": 29.7604267,
    "lng": -95.3698028,
    "city": "Houston"
  },
  {
    "lat": 39.9525839,
    "lng": -75.1652215,
    "city": "Philadelphia"
  },
  {
    "lat": 33.4483771,
    "lng": -112.0740373,
    "city": "Phoenix"
  },
  {
    "lat": 29.4241219,
    "lng": -98.49362819999999,
    "city": "San Antonio"
  },
  {
    "lat": 32.715738,
    "lng": -117.1610838,
    "city": "San Diego"
  },
  {
    "lat": 32.7766642,
    "lng": -96.79698789999999,
    "city": "Dallas"
  },
  {
    "lat": 37.3382082,
    "lng": -121.8863286,
    "city": "San Jose"
  },
  {
    "lat": 30.267153,
    "lng": -97.7430608,
    "city": "Austin"
  },
  {
    "lat": 39.768403,
    "lng": -86.158068,
    "city": "Indianapolis"
  },
  {
    "lat": 30.3321838,
    "lng": -81.65565099999999,
    "city": "Jacksonville"
  },
  {
    "lat": 37.7749295,
    "lng": -122.4194155,
    "city": "San Francisco"
  },
  {
    "lat": 39.9611755,
    "lng": -82.99879419999999,
    "city": "Columbus"
  },
  {
    "lat": 35.2270869,
    "lng": -80.8431267,
    "city": "Charlotte"
  },
  {
    "lat": 32.7554883,
    "lng": -97.3307658,
    "city": "Fort Worth"
  },
  {
    "lat": 42.331427,
    "lng": -83.0457538,
    "city": "Detroit"
  },
  {
    "lat": 31.7775757,
    "lng": -106.4424559,
    "city": "El Paso"
  },
  {
    "lat": 35.1495343,
    "lng": -90.0489801,
    "city": "Memphis"
  },
  {
    "lat": 47.6062095,
    "lng": -122.3320708,
    "city": "Seattle"
  },
  {
    "lat": 39.7392358,
    "lng": -104.990251,
    "city": "Denver"
  },
  {
    "lat": 38.9071923,
    "lng": -77.0368707,
    "city": "Washington"
  },
  {
    "lat": 42.3600825,
    "lng": -71.0588801,
    "city": "Boston"
  },
  {
    "lat": 36.1626638,
    "lng":...