title: get array of parent and all of its child
body: <p>suppose I have this kind of data...</p>
  
  <pre><code>data = [{
      "_id" : "1",
      "parentId" : "thisPostId",
      "topLevelId" : "1",
      "text" : "&lt;p&gt;comment&lt;/p&gt;",
  },
  {
      "_id" : "2",
      "parentId" : "1",
      "topLevelId" : "1",
      "text" : "&lt;p&gt;reply to comment&lt;/p&gt;",
  },
  {
      "_id" : "3",
      "parentId" : "2",
      "topLevelId" : "1",
      "text" : "&lt;p&gt;reply to reply to comment&lt;/p&gt;",
  },
  {
      "_id" : "4",
      "parentId" : "3",
      "topLevelId" : "1",
      "text" : "&lt;p&gt;reply to reply to reply to comment&lt;/p&gt;",
  }]
  </code></pre>
  
  <p>I need to remove a comment and all of its child...</p>
  
  <p>if comment to remove is <code>_id:1</code>,, then I need an array of <code>["1","2","3","4"]</code>,,, then i can run <code>Coll.remove({_id:{$in:["1","2","3","4"]}}, callback);</code></p>
  
  <p>if comment to remove is <code>_id:2</code>,, then I need an array of <code>["2","3","4"]</code></p>
  
  <p>if comment to remove is <code>_id:3</code>,, then I need an array of <code>["3","4"]</code></p>
  
  <p>if comment to remove is <code>_id:4</code>,, then I need an array of <code>["4"]</code></p>
  
  <p>I tried this (with no idea)...</p>
  
  <pre><code>_.forEach(data, function(value, key){
      _.pluck(_.where(key, { "parentId" : "2" }), '_id');
  });
  </code></pre>
  
  <p>and not working...</p>
  
  <p>any help with javascript/lodash/underscore will be appreciated,,,</p>
  
  <p>thank You...</p>