title: Typescript: For in loop over objects won't recognise object's properties
body: <p>I'm using a <code>for in</code> to loop over a list of Meeting-objects called <code>allMeetings</code>. This loop is filling another list called <code>allEvents</code>, where objects other than Meeting will end up in. In that loop I'm trying to get the properties of the Meeting object, but they aren't recognised. I wonder how to solve or bypass it.</p>
  
  <p><em>My Meeting model</em>:</p>
  
  <pre><code>export class Meeting {
      id: UUID;
      date: Date;
      description: string;
  }
  </code></pre>
  
  <p><em>The TS-File</em>: <br>
  <em>The loop is used in the <code>makeEvents()</code> method</em></p>
  
  <pre><code>...
  import { Meeting } from '../models/meeting.model';
  import { MeetingsService } from '../services/meetings.service';
  ...
  export class SomeComponent implements OnInit {
      allEvents: SpikesEvent[] = undefined;
      allMeetings: Meeting[] = undefined;
  
     constructor(private _meetingsService: MeetingsService) { }
  
      ngOnInit() {
          this.loadMeetings();
          this.makeEvents();
      }
  
      loadMeetings(): void {
          this._meetingsService.getAllMeetings().subscribe(
              (allMeetings: Meeting[]) =&gt; {
                  this.allMeetings = allMeetings;
              }
          );
      }
  
      makeEvents(): void {
          for (let meeting in this.allMeetings) {
              this.allEvents.push({
                  start: startOfDay(meeting.date),
                  title: meeting.description,
                  color: colors.yellowsunflower,
                  type: "meeting",
                  id: meeting.id,
              });
          }
      }
  }
  </code></pre>
  
  <p><strong>So, date, description and id of meeting aren't recognised.</strong></p>
  
  <p>EDIT 1: Added the constructor in the TS-File. <br>
  EDIT 2: I'm retrieving my data from rethinkDB so there's no JSON-file but here's a log to prove that the Meeting object is in fact not empty:</p>
  
  <pre><code>date: "Fri Feb 20 1993 00:00:00 GMT+00:00", description: "meeting about dummy data", id: "088c0baf-3c02-48b2-a072-65905fb0c0a7"
  </code></pre>