document.createElement(‘script’);

bodyにscriptを追加。

var script = document.createElement('script');
script.src = 'http://example.com/hoge.js';
document.body.appendChild(script);

window.はdomを収める

mapTypeId: ‘terrain’ 地形情報を使った地図
ROADMAP 道路や建物
SATELITE 衛星写真
HyBRID ROADMAPとSATELITE
TERRAIN 地形情報

デフォルトはROADMAP

<!DOCTYPE html>
<html>
  <head>
    <title>Simple Map</title>
    <meta name="viewport" content="initial-scale=1.0">
    <meta charset="utf-8">
    <style>
      #map {
        height: 50%;
        margin-top: 10px;
      }
      html, body {
        height: 100%;
        margin: 10px;
        padding: 0;
      }
    </style>
  </head>
  <body>
  	<div id="map"></div>
  	<script>
  	var map;
  	function initMap(){
  		map = new google.maps.Map(document.getElementById('map'),{
        zoom: 2,
  			center: new google.maps.LatLng(2.8, -187.3),
        mapTypeId: 'terrain'
  		});

      var script = document.createElement('script');
      script.src = 'https://developers.google.com/maps/documentation/javascript/examples/json/earthquake_GeoJSONP.js';
        document.getElementsByTagName('head')[0].appendChild(script);
      }

      window.eqfeed_callback = function(results) {
        for (var i = 0; i < results.features.length; i++) {
          var coords = results.features&#91;i&#93;.geometry.coordinates;
          var latLng = new google.maps.LatLng(coords&#91;1&#93;,coords&#91;0&#93;);
          var marker = new google.maps.Marker({
            position: latLng,
            map: map
          });
        }
      }
    </script>
  	<script async defer
src = "https:maps.googleapis.com/maps/api/js?key=notwatchk&callback=initMap">
</script>
</body>
</html>