Node JS Mongoose 异步回调

我有这段代码，我似乎有点糊涂了。它所做的是创建用户。现在，如果用户拥有公司，则该公司应与用户一起创建并相应地链接。如果公司已经存在，则不应创建它，也不应将其归因于用户。

首先，代码查找一家公司，如果找不到，则创建一家公司。生活很好。但是，如果我要在“if (!company)”检查中添加一个 else，我将复制大部分创建用户代码。我也相信我无法检查公司然后同步运行用户创建，就像我通常用不同的语言所做的那样。因此我有点卡住了..

module.exports = {
  postUsers: (req, res) => {
    'use strict'
    Company.findOne({name: req.body.company}, (err, company) => {
      if (err) {
        Logger.error(err)
        return res.send(500, err)
      }
      if (!company) {
        // only attribute a company if one doesn't exist
        // don't want users to assign themselves to existing companies automatically
        // need approval in place from an existing company member
        let newCompanyToAdd = new Company({
          name: req.body.company
        })
        newCompanyToAdd.save(err => {
          if (err) {
            Logger.error(err)
            return res.send(500, err)
          }
          let user = new User({
            username: req.body.username,
            password: req.body.password,
            firstname: req.body.firstname,
            lastname: req.body.lastname,
            company: newCompanyToAdd.id
          })
          user.save(err => {
            if (err) {
              return res.send(500, err)
            }
            res.status(200).json({ message: 'New User Added' })
          })
        })
      }
    })
  }

编辑＃

  postUsers: (req, res) => {
    'use strict'
    let user = new User({
      username: req.body.username,
      password: req.body.password,
      firstname: req.body.firstname,
      lastname: req.body.lastname
    })
    Company.findOne({name: req.body.company}, (err, company) => {
      if (err) {
        Logger.error(err)
        return res.send(500, err)
      }
      if (!company && req.name.company !== undefined) {
        // only attribute a company if one doesn't exist
        // don't want users to assign themselves to existing companies automatically
        // need approval in place from an existing company member
        let newCompanyToAdd = new Company({
          name: req.body.company
        })
        newCompanyToAdd.save(err => {
          if (err) {
            Logger.error(err)
            return res.send(500, err)
          }
          user.company = newCompanyToAdd._id
        })
      }
    })
    user.save(err => {
      if (err) {
        return res.send(500, err)
      }
      res.status(200).json({ message: 'New User Added' })
    })
  }