gistfile1.txt

 //variable data is JSON string
 
 db.collection('objects').update({
            _key: key,
            'secretary.username': options.username
        }, {
            $addToSet: {
                "secretary.$" : data
            }
        }, {
            upsert: true, w: 1
        },  function(err, result) {
            if (err) {
                return cb(err, null);
            }
              return cb(null, result);
        });