Node.js ERR_STREAM_WRITE_AFTER_END错误原因及解决方法

问题现象 #

创建http1.js文件后，访问localhost:5000能正常返回内容，但访问localhost:5000/about时浏览器显示localhost拒绝连接，控制台抛出以下错误：

node:events:490
        throw er; // Unhandled 'error' event
        ^
  
  Error [ERR_STREAM_WRITE_AFTER_END]: write after end
      at new NodeError (node:internal/errors:399:5)
      at ServerResponse.end (node:_http_outgoing:1009:15)
      at Server.<anonymous> (c:\Users\Suresh\pratice_Tuotorial(JN)\.vscode\tempCodeRunnerFile.js:9:9)
      at Server.emit (node:events:512:28)
      at parserOnIncoming (node:_http_server:1086:12)
      at HTTPParser.parserOnHeadersComplete (node:_http_common:119:17)
  Emitted 'error' event on ServerResponse instance at:
      at emitErrorNt (node:_http_outgoing:849:9)
      at process.processTicksAndRejections (node:internal/process/task_queues:83:21) {
    code: 'ERR_STREAM_WRITE_AFTER_END'
  }

原代码 #

const http = require('http')
const server = http.create Server((req, res) => {

    if (req.url === '/') {
        res.end('Welcome to our home page')
    }
    if (req.url === '/about') {
        res.end('Here is our short history')
    }

    res.end(
        `<h1>Oops!</h1>
         <p>We can't seem to find the page your are looking for</p>
         <a  h ref ="/">Back home page</a>`
    )

})
server.listen(5000)

问题原因 #

1. 重复调用res.end()：两个独立的if语句没有阻止后续代码执行，当请求匹配/或/about时，执行完对应res.end()后，代码仍会走到最后的res.end()。HTTP响应流在第一次res.end()后就会关闭，再次调用直接触发write after end错误，导致服务器进程崩溃，浏览器因此显示连接被拒绝。
2. 语法小错误：http.create Server存在空格，正确写法应为http.createServer。

解决办法 #

有两种修复方式，同时修正代码里的小问题：

方式1：使用if-else if-else结构 #

确保只有一个res.end()会被执行：

const http = require('http')
const server = http.createServer((req, res) => {
    if (req.url === '/') {
        res.end('Welcome to our home page')
    } else if (req.url === '/about') {
        res.end('Here is our short history')
    } else {
        res.end(
            `<h1>Oops!</h1>
             <p>We can't seem to find the page you are looking for</p>
             <a href="/">Back to home page</a>`
        )
    }
})
server.listen(5000)

方式2：在每个if块内添加return #

执行完res.end()后直接返回，终止后续代码运行：

const http = require('http')
const server = http.createServer((req, res) => {
    if (req.url === '/') {
        res.end('Welcome to our home page')
        return
    }
    if (req.url === '/about') {
        res.end('Here is our short history')
        return
    }

    res.end(
        `<h1>Oops!</h1>
         <p>We can't seem to find the page you are looking for</p>
         <a href="/">Back to home page</a>`
    )
})
server.listen(5000)

额外修正了HTML里的h ref拼写错误（改为href）和your的语法错误（改为you）。

内容的提问来源于stack exchange，提问作者Vaishnavi