title: How to iterate an array in object with unknown key
body: <p>I would like to the iterate the array in this object:</p>
  
  <pre><code>obj = {'2012-01-01':[1,2,5,8]}
  </code></pre>
  
  <p>I understand we can iterate like this:</p>
  
  <pre><code>   for(var i = 0;i &lt; obj.length;i++){
      obj['2012-08-08'][i]
      }
  </code></pre>
  
  <p>But if it is not known the name of the key how we iterate the array?</p>
  
  <p>Say I have a loop:</p>
  
  <pre><code>_.each(dates, function(date){
       //each date is like the above javascript object, how to  iterate the array?
  
  })
  </code></pre>