title: How to resolve undefined google.maps.mapTypeId.ROADMAP issue when implementing Google Maps in Ionic app?
body: <p>I am trying to display google maps in my ionic app.</p>
  
  <p>The map is displaying, but when I try to add this <code>mapTypeId: google.maps.mapTypeId.ROADMAP</code> to my mapOptions below:</p>
  
  <pre><code>loadMap() {
      let latLng = new google.maps.LatLng(51.9036442, 7.6673267);
  
      let mapOptions = {
          center: latLng,
          zoom: 5,
          // mapTypeId: google.maps.mapTypeId.ROADMAP
      };
      this.map = new google.maps.Map(this.mapElement.nativeElement, mapOptions);
  }
  </code></pre>
  
  <p>I get the following error:</p>
  
  <blockquote>
    <p>ERROR TypeError: Cannot read property 'ROADMAP' of undefined
        at HomePage.loadMap </p>
  </blockquote>
  
  <p>Can someone please tell me how to resolve this issue?</p>