What I want to achieve is to operate the reply - save table and the topic table at the same time after user, and then return them together. I don’t know how to use promise.all to wrap these two query update operations. I hope you can help me solve it. = =

Update: The following is the modified version.

/* 回复 话题 */
router.post('/reply', (req, res, next) => {
  let topic_id = req.body.topic_id,
      content  = req.body.content

  let replyEntity = new replyModel({
    author: req._id,
    topic: topic_id,
    content
  })

  replyEntity.save()
             .then((_new_reply) => {
                Promise.all([
                  topicModel.findByIdAndUpdate(topic_id, {
                    $inc: {replyNum: 1},
                    last_reply_author: req._id,
                    last_reply_time: Date.now()
                  }),
                  userModel.findByIdAndUpdate(req._id, {
                    $push: {replies: _new_reply._id}
                  })
                ])
                .then((res_arr) => {
                  return res.json({
                    status: 0
                  })
                })
                .catch((err) => {
                  return res.json({
                    status: -1
                  })
                })
             })
             .catch((err) => {
                return res.json({
                  status: -1
                })
             })
})