Populate grandchildren in arrays, Mongoose 3.8.x

gistfile1.txt

Parent.findById(req.params._id).populate('children').exec(function(err, doc){
// note that you have to populate the children here
// or they won't turn up properly later
// even if you substitute all of them with a new document set.
	Child.find({'_parent':req.params._id}).populate('grandchildren').exec(function(err, docs){
	// note that the child has to know it belongs to the parent in its own schema
	// this is technically a totally separate document set.
		if(err) res.send(err);

		Child.populate(docs, {path: 'grandchildren.greatGrandChildren', model:'GreatGrandChild'}, function(err, data){
		// now that you have the technically separate top-level doc set
		// you can populate the subdocs and they'll go out just fine.
				parent.children = data;
				res.json({'parent' : parent})
		})
	});
});