javascript - Express Promise Chain如何发送响应并结束Promise Chain流程？

Question

使用下面的代码我收到此错误:

未处理的拒绝错误 [ERR_HTTP_HEADERS_SENT]:如果 result === null，则在将 header 发送到客户端后无法设置 header 。

'use strict'

const HttpStatus = require('http-status-codes')
const { handleErr } = require('ciitizen-express-helpers').utils

function updateOrganization(db, stats) {
  return function (req, res) {
    db.organization.findOne({
      where: {
        id: req.params.id
      }
    })
      .then(result => {

        if (result === null) {
          return res.status(HttpStatus.NOT_FOUND).send() <-- IF RESULT IS NULL, I RETURN THIS 
        }

        console.log('original result = ', result)

        // Update any fields that were passed in
        if (req.body.name) {
          result.name = req.body.name
        }

        if (req.body.address1) {
          result.address1 = req.body.address1
        }

        if (req.body.address2) {
          result.address2 = req.body.address2
        }

        if (req.body.city) {
          result.city = req.body.city
        }

        if (req.body.state) {
          result.state = req.body.state
        }

        if (req.body.zip) {
          result.zip = req.body.zip
        }

        console.log('new result = ', result)
        return result.save()
      })
      .then(result => {
        console.log('final result = ', result)
        return res.status(HttpStatus.CREATED).send(result) <-- BUT IT'S STILL TRYING TO CALL THIS, HENCE THE CAN'T SEND HEADERS ERROR
      })
      .catch(err => {
        req.log.error(err)
        return handleErr(res, HttpStatus.INTERNAL_SERVER_ERROR, err.message)
      })
  }
}

module.exports = updateOrganization

在不继续我的 promise 链流程的情况下提前返回响应的最佳方式是什么？

Answer 1

像这样的 promise 链

你能做的是

A) res.status(HttpStatus.NOT_FOUND) 之后return null(删除该代码之前的return)

B) in then(result) 检查 result 是否为 null，如果是，则跳过 res.status(... 代码

例如

'use strict'

const HttpStatus = require('http-status-codes')
const { handleErr } = require('ciitizen-express-helpers').utils

function updateOrganization(db, stats) {
  return function (req, res) {
    db.organization.findOne({
      where: {
        id: req.params.id
      }
    })
      .then(result => {

        if (result === null) {
          // change A
          res.status(HttpStatus.NOT_FOUND).send();
          return null;
        }
        // snip
        return result.save()
      })
      .then(result => {
        console.log('final result = ', result)
        // change B
        if (result !== null) {
            return res.status(HttpStatus.CREATED).send(result)
        }
      })
      .catch(err => {
        req.log.error(err)
        return handleErr(res, HttpStatus.INTERNAL_SERVER_ERROR, err.message)
      })
  }
}

module.exports = updateOrganization

或者，保留现有代码直到

      .then(result => {
        // change C
        if (!res.headersSent) {
            console.log('final result = ', result)
            return res.status(HttpStatus.CREATED).send(result)
        }
      })

说实话，这可能是一个“更干净”的修复