title: Enumerate properties on an object
body: <p>Given the following class, how can I enumerate its properties, i.e. get an output like <code>[station1, station2, station3 ...]</code>?</p>
  
  <p>I can only see how to enumerate the values of the properties, i.e. <code>[null, null, null]</code>.</p>
  
  <pre><code>class stationGuide {
      station1: any;
      station2: any;
      station3: any;
  
      constructor(){
          this.station1 = null;
          this.station2 = null;
          this.station3 = null;
       }
  }
  </code></pre>