title: Pull multiple values from array with mongo node native driver
body: <p>The problem is :</p>
  
  <pre><code>doc1:{ 
    _id:1,
    array:['a','b','c']
  },
  doc2:{ 
    _id:2,
    array:['a','f','c']
  }
  </code></pre>
  
  <p>I'm trying to remove <code>['a','b']</code> from the <code>array</code> field, using :</p>
  
  <p><code>.update({_id:1},{$pull:{array:['a','b']}})</code> but it doesn't seem to change anything, is there a different function I should use?</p>