title: how to use/integrate google maps apis in angular 4
body: <pre><code>how to use google maps apis in angular 4.
  </code></pre>
  
  <p>I am trying to use google maps.
      gave reference to <strong>google maps api</strong> with the key.
      but not able to use it.
      while integrating it . got the error google is not defined and to resolve i declared var google:any 
      error got resolved but it is not building the map and now i am getting 
      "Cannot read property 'firstChild' of null"</p>