title: Loop through an object starting at an index
body: <p>I have an object that is a list of chatrooms, where the keys are chat room names and the value is a reference to the chat room. I want to deliver the rooms to users 50 rooms at a time. But I don't see how this can be done with an object.</p>
  
  <p>Suppose you want to loop through</p>
  
  <pre><code>var obj = {
     "a" : 1,
     "b" : 2.
     "c" : 3
  }
  </code></pre>
  
  <p>But start at "b", ending up with only "b" and "c" being accessed. Can it be done, including using some kind of map or table? </p>