title: Return updated collection with Mongoose
body: <p>I work with nodejs/express/mongoose/angularjs. I'd like to update a collection named Lists which has several properties, one of which is an array of items. In the following code, I'm pushing a new task items in the items array. Everything works fine, however the update function does not sends back the updated collection, then I must perform another query on the database. Is there a more efficient way to do this ? </p>
  
  <p><strong>The nodejs/express code :</strong></p>
  
  <pre><code>exports.addTaskToList = function(req, res) {
      var listId = req.params.Id;
      var taskId = req.params.TaskId;
      Lists.update({_id: listId}, {$push: {items: taskId}}, {safe:true, upsert: true}, function(err, result){
          if(err) {
              console.log('Error updating todo list. ' + err);
          }
          else{
              console.log(result + ' todo list entry updated - New task added');
              Lists.findById(listId).populate('items').exec(function (err, updatedEntry) {
                  if (err) {
                      console.log('Unable to retrieve todo list entry.');
                  }
                  res.send(JSON.stringify(updatedEntry));
              });
          }           
      });
  };
  </code></pre>
  
  <p>Furthermore, the array items is an array of ObjectIds. Those items are in a separate schema so in a separate collection. Is it possible to push the whole object and not only its _id so that there is not another collection created ?</p>