title: window.Map is not a constructor in Google Maps API v3
body: <p>I have a google map with a new key</p>
  
  <p>but it gets error in console</p>
  
  <p>error:</p>
  
  <pre><code>Uncaught TypeError: window.Map is not a constructor
      at Zr (map.js:2)
      at ds.release (map.js:53)
      at gs (map.js:5)
      at _.rl.Ab (map.js:59)
      at map.js:46
  </code></pre>
  
  <p>HTML</p>
  
  <pre><code>&lt;head&gt;
  &lt;script async defer
          src="https://maps.googleapis.com/maps/api/js?key=mykey"&gt;
  &lt;/script&gt;
  &lt;/head&gt;
  
  &lt;body onload="init()"&gt;
      &lt;div id="map_canvas"&gt;&lt;/div&gt;
  &lt;/body&gt;
  &lt;script src="js/index.js"&gt;&lt;/script&gt;
  </code></pre>
  
  <p>index.js</p>
  
  <pre><code>Map = null;
  function init() {
      var mapOptions = {***};
      Map = new google.maps.Map( document.getElementById( "map_canvas" ), mapOptions );
  }
  </code></pre>
  
  <p>Thanks for your time!</p>