title: Socket io: Cannot for loop or use array methods on socket.rooms
body: <p>I want to write:</p>
  <pre><code>socket.on(&quot;create-room&quot;, (roomID)=&gt; socket.room = roomID)
  
  let userS_selected_room = 'f2eac135-eafd-49e1-adc7-c89351703896';
  
  for(room in socket.rooms){
    if(room === userS_selected_room) {do_stuff()}
  }
  </code></pre>
  <p>I don't understand these:  Map(4), [Set]</p>
  <p>console.log(socket.rooms)</p>
  <pre><code>Set(4) {
    'zBROv1Lug0XhoQxCAAAB',
    'room1',
    '9e9ecaa6-473a-43a6-9ab7-60ff034ab614',
    '1dc1547c-d265-4d5a-bd3f-9a5d37bf883a'
  }
  </code></pre>
  <p>console.log(socket)/</p>
  <pre><code>...
      rooms: Map(4) {
        '6Otk--hk5SHOVRcrAAAD' =&gt; [Set], //socket id 
        'room1' =&gt; [Set],
        'f2eac135-eafd-49e1-adc7-c89351703896' =&gt; [Set], //this is room id
        '91fdf074-a1e7-493b-97b9-5a6050095697' =&gt; [Set] //this is room id
      },
  ...
  </code></pre>