Mongoose - markModified

mongoose中使用save方法修改嵌套数据时，添加order.markModified(‘checkResult’);这句，以完成修改操作，否则无法修改嵌套数据。

order = _.merge(order, req.body);
order.markModified('checkResult');
order.save()
     .then(() => {
         return res.send({code: '400000', messageInfo: ['The update was successful.']});
     })
     .catch(err => next(err));