Node.js心得笔记

npm init 可用npm 来调试node项目

浏览器中的顶级对象时window

<ref *1> Object [global] { global: [Circular *1], clearImmediate: [Function: clearImmediate], setImmediate: [Function: setImmediate] { [Symbol(nodejs.util.promisify.custom)]: [Getter] }, clearInterval: [Function: clearInterval], clearTimeout: [Function: clearTimeout], setInterval: [Function: setInterval], setTimeout: [Function: setTimeout] { [Symbol(nodejs.util.promisify.custom)]: [Getter] }, queueMicrotask: [Function: queueMicrotask], structuredClone: [Function: structuredClone], atob: [Getter/Setter], btoa: [Getter/Setter], performance: [Getter/Setter], fetch: [Function: fetch], crypto: [Getter] }

node中的顶级对象时global

module.exports 与 require

const GetName = ()=>{ return "jack" ; }; const GetAge = ()=>{ return 18; }; module.exports = { GetName, GetAge }

const {GetName,GetAge} = require("./utils"); GetName(); GetAge();

默认情况下，Node.js 将 JavaScript 文件视为 CommonJS 模块,需要使用:module.exports ={} 和 require 来导出导入。若使用export 与 import 报错，需要将package.js中的:"type": "commonjs", 转成 type": "module"

export default = methods 更适用于单个组件进行导出，可以随意命名，并且一个js文件中只能有一个默认导出

export = {...methods} 更适用于多个方法的导出，不能随意命名，但可以通过 import {methodName as methodSetName} 来进行命名，一个js文件中可有多个普通导出

值得注意的是，在一个js文件中，可以同时有多个普通导出与一个默认导出。

后端server配置CORS ，允许前端跨域发起请求

同源策略是一个安全机制，要求“协议+域名+端口”三者相同，否则浏览器会阻止网页向不同源的服务器发送请求。

// Add CORS headers,允许跨域 res.setHeader('Access-Control-Allow-Origin', 'http://localhost:5173'); //'http://localhost:5173/' 会报错，不能加，因为这个CORS是根据字符串来匹配的 // 允许所有源 res.setHeader('Access-Control-Allow-Origin', '*'); // 也可以根据请求源动态设置，允许信任的请求源 const allowedOrigins = ['http://localhost:5173', 'https://yourapp.com', 'http://127.0.0.1:8080']; const origin = req.headers.origin; if (allowedOrigins.includes(origin)) { res.setHeader('Access-Control-Allow-Origin', origin); } res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS, PUT, DELETE'); res.setHeader('Access-Control-Allow-Headers', 'Content-Type, Authorization');

若前端在请求头中自定义了某个属性，你需要在后台服务器中的CORS也定义上：

//前端 axios.get('http://localhost:8888/', { headers: { 'X-Custom-Header': 'foobar' } }) //后台服务器 res.setHeader('Access-Control-Allow-Headers','Content-Type, Authorization, X-Custom-Header');

避免修改一次代码就要重启一次服务器

npm install nodemon

package-lock.js 是依赖项文件夹，类似于python中的requirement.txt,执行npm install 可下载所有的依赖项。并会将所有的依赖项存储到文件夹node_modules里。同时，npm i 也能完成更新依赖包的作用。作用是为了防止将依赖包都放到github上

也可以在.gitignore中添加不推送到github中的文件夹/文件名

.gitignore | node_modules | ...all_requirement_packages

配置package.json文件，完成使用nodemon 来调试程序。

"scripts": { "test": "echo \"Error: no test specified\" && exit 1", "start": "nodemon server.js", "dev": "nodemon server.js" },

.env文件

用于设置项目中的全局变量,不能有空格

PORT=8080

//实际使用 const PORT = process.env.PORT;

"scripts": { "test": "echo \"Error: no test specified\" && exit 1", "start": "nodemon server.js", "dev": "nodemon --env-file=.env server.js" },

必须要加 --env-file=.env，否则指定的全局变量会显示undefined

并且可以在.gitignore文件中，添加.env ，防止上传到git

原生的node.js服务端

import http from 'http'; // const PORT = process.end.PORT; const PORT = process.env.PORT; const server = http.createServer((req, res) => { // Add CORS headers,解决跨域问题 res.setHeader('Access-Control-Allow-Origin', 'http://localhost:5173'); res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS, PUT, DELETE'); res.setHeader('Access-Control-Allow-Headers', 'Content-Type, Authorization, X-Custom-Header'); //debug console.log(req.url); //客户端请求的网址 console.log(req.method); //客户端的请求方式 // For normal requests, proceed with your existing code res.writeHead(200, "OK", { 'Content-Type': 'text/html' }); res.write( `<h1>hello user</h1> <h2>Welcome to http my server</h2> <h3>Wish you have a good day</h3> ` ); res.end(JSON.stringify({ "message": "ok", "statusCode": 200, "data": { "name": "Jack", "age": 18, "home":"ShangHai", } })); }); server.listen(PORT, () => { console.log(`use ${PORT} port ,search: http://localhost:${PORT}/`); });

客户端像后端发起get请求，为什么后台打印：OPTIONS GET

这是由于：CORS预检机制

当浏览器发起跨域请求时，会触发CORS（跨源资源共享）机制。在特定情况下，浏览器会在实际请求前自动发送一个"预检请求"（OPTIONS请求），这就是您在后台看到OPTIONS和GET两个请求的原因。

关于Access-Control-Max-Age的详细说明

这个头部信息的作用是告诉浏览器在指定的时间内（以秒为单位）可以缓存预检请求的结果，而无需再次发送OPTIONS请求。这对于优化性能非常有益，特别是在频繁发生跨域请求的应用中。

浏览器限制：不同浏览器对Access-Control-Max-Age的最大值有不同限制：

• Chrome: 最大值为7200秒（2小时）

• Firefox: 最大值为86400秒（24小时）

• Safari: 没有明确限制，但遵循标准建议

将获取当前文件的路径

import fs from 'fs/promises'; import url from 'url'; import path from 'path'; //get current path //import.meta.url 当前路径的url export const GetCurrentPath = (importUrl) =>{ const fileName = url.fileURLToPath(importUrl); //将文件的url转化为路径 const dirName = path.dirname(fileName); //输入:文件的路径;输出:文件所在目录 return { fileName, dirName } } console.log(import.meta.url); //file:///C:/Users/32217/Desktop/%E9%A1%B9%E7%9B%AE/%E5%8C%BB%E7%96%97%E5%81%A5%E5%BA%B7%E7%AE%A1%E7%90%86%E7%B3%BB%E7%BB%9F/code/front-end/server.js console.log(fileName); console.log(dirName); /* C:\Users\32217\Desktop\项目\医疗健康管理系统\code\front-end\server.js C:\Users\32217\Desktop\项目\医疗健康管理系统\code\front-end */

response.writeHead() 与 response.end() 必须配套使用，否则会响应超时！！！

Request

C:\Users\32217\Desktop\项目\医疗健康管理系统\code\front-end\public\404.html Using port 8888, visit: http://localhost:8888/ req.url:/Login req.method:POST <ref *2> IncomingMessage { _events: { close: undefined, error: undefined, data: undefined, end: undefined, readable: undefined }, _readableState: ReadableState { highWaterMark: 16384, buffer: [], bufferIndex: 0, length: 0, pipes: [], awaitDrainWriters: null, [Symbol(kState)]: 1315084 }, _maxListeners: undefined, socket: <ref *1> Socket { connecting: false, _hadError: false, _parent: null, _host: null, _closeAfterHandlingError: false, _events: { close: [Array], error: [Function: socketOnError], prefinish: undefined, finish: undefined, drain: [Function: bound socketOnDrain], data: [Function: bound socketOnData], end: [Array], readable: undefined, timeout: [Function: socketOnTimeout], resume: [Function: onSocketResume], pause: [Function: onSocketPause] }, _readableState: ReadableState { highWaterMark: 16384, buffer: [], bufferIndex: 0, length: 0, pipes: [], awaitDrainWriters: null, [Symbol(kState)]: 193997060 }, _writableState: WritableState { highWaterMark: 16384, length: 0, corked: 0, onwrite: [Function: bound onwrite], writelen: 0, bufferedIndex: 0, pendingcb: 0, [Symbol(kState)]: 17564420, [Symbol(kBufferedValue)]: null }, allowHalfOpen: true, _maxListeners: undefined, _eventsCount: 8, _sockname: null, _pendingData: null, _pendingEncoding: '', server: Server { maxHeaderSize: undefined, insecureHTTPParser: undefined, requestTimeout: 300000, headersTimeout: 60000, keepAliveTimeout: 5000, connectionsCheckingInterval: 30000, requireHostHeader: true, joinDuplicateHeaders: undefined, rejectNonStandardBodyWrites: false, _events: [Object: null prototype], _eventsCount: 3, _maxListeners: undefined, _connections: 1, _handle: [TCP], _usingWorkers: false, _workers: [], _unref: false, _listeningId: 2, allowHalfOpen: true, pauseOnConnect: false, noDelay: true, keepAlive: false, keepAliveInitialDelay: 0, highWaterMark: 16384, httpAllowHalfOpen: false, timeout: 0, maxHeadersCount: null, maxRequestsPerSocket: 0, _connectionKey: '6::::8888', [Symbol(IncomingMessage)]: [Function: IncomingMessage], [Symbol(ServerResponse)]: [Function: ServerResponse], [Symbol(shapeMode)]: false, [Symbol(kCapture)]: false, [Symbol(async_id_symbol)]: 245, [Symbol(kUniqueHeaders)]: null, [Symbol(http.server.connections)]: ConnectionsList {}, [Symbol(http.server.connectionsCheckingInterval)]: Timeout { _idleTimeout: 30000, _idlePrev: [TimersList], _idleNext: [TimersList], _idleStart: 191, _onTimeout: [Function: bound checkConnections], _timerArgs: undefined, _repeat: 30000, _destroyed: false, [Symbol(refed)]: false, [Symbol(kHasPrimitive)]: false, [Symbol(asyncId)]: 248, [Symbol(triggerId)]: 246 } }, _server: Server { maxHeaderSize: undefined, insecureHTTPParser: undefined, requestTimeout: 300000, headersTimeout: 60000, keepAliveTimeout: 5000, connectionsCheckingInterval: 30000, requireHostHeader: true, joinDuplicateHeaders: undefined, rejectNonStandardBodyWrites: false, _events: [Object: null prototype], _eventsCount: 3, _maxListeners: undefined, _connections: 1, _handle: [TCP], _usingWorkers: false, _workers: [], _unref: false, _listeningId: 2, allowHalfOpen: true, pauseOnConnect: false, noDelay: true, keepAlive: false, keepAliveInitialDelay: 0, highWaterMark: 16384, httpAllowHalfOpen: false, timeout: 0, maxHeadersCount: null, maxRequestsPerSocket: 0, _connectionKey: '6::::8888', [Symbol(IncomingMessage)]: [Function: IncomingMessage], [Symbol(ServerResponse)]: [Function: ServerResponse], [Symbol(shapeMode)]: false, [Symbol(kCapture)]: false, [Symbol(async_id_symbol)]: 245, [Symbol(kUniqueHeaders)]: null, [Symbol(http.server.connections)]: ConnectionsList {}, [Symbol(http.server.connectionsCheckingInterval)]: Timeout { _idleTimeout: 30000, _idlePrev: [TimersList], _idleNext: [TimersList], _idleStart: 191, _onTimeout: [Function: bound checkConnections], _timerArgs: undefined, _repeat: 30000, _destroyed: false, [Symbol(refed)]: false, [Symbol(kHasPrimitive)]: false, [Symbol(asyncId)]: 248, [Symbol(triggerId)]: 246 } }, parser: HTTPParser { '0': null, '1': [Function: parserOnHeaders], '2': [Function: parserOnHeadersComplete], '3': [Function: parserOnBody], '4': [Function: parserOnMessageComplete], '5': [Function: bound onParserExecute], '6': [Function: bound onParserTimeout], _headers: [], _url: '', socket: [Circular *1], incoming: [Circular *2], outgoing: null, maxHeaderPairs: 2000, _consumed: true, onIncoming: [Function: bound parserOnIncoming], joinDuplicateHeaders: null, [Symbol(resource_symbol)]: [HTTPServerAsyncResource] }, on: [Function: socketListenerWrap], addListener: [Function: socketListenerWrap], prependListener: [Function: socketListenerWrap], setEncoding: [Function: socketSetEncoding], _paused: false, _httpMessage: ServerResponse { _events: [Object: null prototype], _eventsCount: 1, _maxListeners: undefined, outputData: [], outputSize: 0, writable: true, destroyed: false, _last: false, chunkedEncoding: false, shouldKeepAlive: true, maxRequestsOnConnectionReached: false, _defaultKeepAlive: true, useChunkedEncodingByDefault: true, sendDate: true, _removedConnection: false, _removedContLen: false, _removedTE: false, strictContentLength: false, _contentLength: null, _hasBody: true, _trailer: '', finished: false, _headerSent: false, _closed: false, socket: [Circular *1], _header: null, _keepAliveTimeout: 5000, _onPendingData: [Function: bound updateOutgoingData], req: [Circular *2], _sent100: false, _expect_continue: false, _maxRequestsPerSocket: 0, [Symbol(shapeMode)]: false, [Symbol(kCapture)]: false, [Symbol(kBytesWritten)]: 0, [Symbol(kNeedDrain)]: false, [Symbol(corked)]: 0, [Symbol(kOutHeaders)]: [Object: null prototype], [Symbol(errored)]: null, [Symbol(kHighWaterMark)]: 16384, [Symbol(kRejectNonStandardBodyWrites)]: false, [Symbol(kUniqueHeaders)]: null }, [Symbol(async_id_symbol)]: 250, [Symbol(kHandle)]: TCP { reading: true, onconnection: null, _consumed: true, [Symbol(owner_symbol)]: [Circular *1] }, [Symbol(lastWriteQueueSize)]: 0, [Symbol(timeout)]: null, [Symbol(kBuffer)]: null, [Symbol(kBufferCb)]: null, [Symbol(kBufferGen)]: null, [Symbol(shapeMode)]: true, [Symbol(kCapture)]: false, [Symbol(kSetNoDelay)]: true, [Symbol(kSetKeepAlive)]: false, [Symbol(kSetKeepAliveInitialDelay)]: 0, [Symbol(kBytesRead)]: 0, [Symbol(kBytesWritten)]: 0 }, httpVersionMajor: 1, httpVersionMinor: 1, httpVersion: '1.1', complete: false, rawHeaders: [ 'Host', 'localhost:8888', 'Connection', 'keep-alive', 'Content-Length', '45', 'sec-ch-ua-platform', '"Windows"', 'User-Agent', 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/135.0.0.0 Safari/537.36', 'Accept', 'application/json, text/plain, */*', 'sec-ch-ua', '"Google Chrome";v="135", "Not-A.Brand";v="8", "Chromium";v="135"', 'Content-Type', 'application/json', 'X-Custom-Header', 'foobar', 'sec-ch-ua-mobile', '?0', 'Origin', 'http://localhost:5173', 'Sec-Fetch-Site', 'same-site', 'Sec-Fetch-Mode', 'cors', 'Sec-Fetch-Dest', 'empty', 'Referer', 'http://localhost:5173/', 'Accept-Encoding', 'gzip, deflate, br, zstd', 'Accept-Language', 'zh-CN,zh;q=0.9' ], rawTrailers: [], joinDuplicateHeaders: null, aborted: false, upgrade: false, url: '/Login', method: 'POST', statusCode: null, statusMessage: null, client: <ref *1> Socket { connecting: false, _hadError: false, _parent: null, _host: null, _closeAfterHandlingError: false, _events: { close: [Array], error: [Function: socketOnError], prefinish: undefined, finish: undefined, drain: [Function: bound socketOnDrain], data: [Function: bound socketOnData], end: [Array], readable: undefined, timeout: [Function: socketOnTimeout], resume: [Function: onSocketResume], pause: [Function: onSocketPause] }, _readableState: ReadableState { highWaterMark: 16384, buffer: [], bufferIndex: 0, length: 0, pipes: [], awaitDrainWriters: null, [Symbol(kState)]: 193997060 }, _writableState: WritableState { highWaterMark: 16384, length: 0, corked: 0, onwrite: [Function: bound onwrite], writelen: 0, bufferedIndex: 0, pendingcb: 0, [Symbol(kState)]: 17564420, [Symbol(kBufferedValue)]: null }, allowHalfOpen: true, _maxListeners: undefined, _eventsCount: 8, _sockname: null, _pendingData: null, _pendingEncoding: '', server: Server { maxHeaderSize: undefined, insecureHTTPParser: undefined, requestTimeout: 300000, headersTimeout: 60000, keepAliveTimeout: 5000, connectionsCheckingInterval: 30000, requireHostHeader: true, joinDuplicateHeaders: undefined, rejectNonStandardBodyWrites: false, _events: [Object: null prototype], _eventsCount: 3, _maxListeners: undefined, _connections: 1, _handle: [TCP], _usingWorkers: false, _workers: [], _unref: false, _listeningId: 2, allowHalfOpen: true, pauseOnConnect: false, noDelay: true, keepAlive: false, keepAliveInitialDelay: 0, highWaterMark: 16384, httpAllowHalfOpen: false, timeout: 0, maxHeadersCount: null, maxRequestsPerSocket: 0, _connectionKey: '6::::8888', [Symbol(IncomingMessage)]: [Function: IncomingMessage], [Symbol(ServerResponse)]: [Function: ServerResponse], [Symbol(shapeMode)]: false, [Symbol(kCapture)]: false, [Symbol(async_id_symbol)]: 245, [Symbol(kUniqueHeaders)]: null, [Symbol(http.server.connections)]: ConnectionsList {}, [Symbol(http.server.connectionsCheckingInterval)]: Timeout { _idleTimeout: 30000, _idlePrev: [TimersList], _idleNext: [TimersList], _idleStart: 191, _onTimeout: [Function: bound checkConnections], _timerArgs: undefined, _repeat: 30000, _destroyed: false, [Symbol(refed)]: false, [Symbol(kHasPrimitive)]: false, [Symbol(asyncId)]: 248, [Symbol(triggerId)]: 246 } }, _server: Server { maxHeaderSize: undefined, insecureHTTPParser: undefined, requestTimeout: 300000, headersTimeout: 60000, keepAliveTimeout: 5000, connectionsCheckingInterval: 30000, requireHostHeader: true, joinDuplicateHeaders: undefined, rejectNonStandardBodyWrites: false, _events: [Object: null prototype], _eventsCount: 3, _maxListeners: undefined, _connections: 1, _handle: [TCP], _usingWorkers: false, _workers: [], _unref: false, _listeningId: 2, allowHalfOpen: true, pauseOnConnect: false, noDelay: true, keepAlive: false, keepAliveInitialDelay: 0, highWaterMark: 16384, httpAllowHalfOpen: false, timeout: 0, maxHeadersCount: null, maxRequestsPerSocket: 0, _connectionKey: '6::::8888', [Symbol(IncomingMessage)]: [Function: IncomingMessage], [Symbol(ServerResponse)]: [Function: ServerResponse], [Symbol(shapeMode)]: false, [Symbol(kCapture)]: false, [Symbol(async_id_symbol)]: 245, [Symbol(kUniqueHeaders)]: null, [Symbol(http.server.connections)]: ConnectionsList {}, [Symbol(http.server.connectionsCheckingInterval)]: Timeout { _idleTimeout: 30000, _idlePrev: [TimersList], _idleNext: [TimersList], _idleStart: 191, _onTimeout: [Function: bound checkConnections], _timerArgs: undefined, _repeat: 30000, _destroyed: false, [Symbol(refed)]: false, [Symbol(kHasPrimitive)]: false, [Symbol(asyncId)]: 248, [Symbol(triggerId)]: 246 } }, parser: HTTPParser { '0': null, '1': [Function: parserOnHeaders], '2': [Function: parserOnHeadersComplete], '3': [Function: parserOnBody], '4': [Function: parserOnMessageComplete], '5': [Function: bound onParserExecute], '6': [Function: bound onParserTimeout], _headers: [], _url: '', socket: [Circular *1], incoming: [Circular *2], outgoing: null, maxHeaderPairs: 2000, _consumed: true, onIncoming: [Function: bound parserOnIncoming], joinDuplicateHeaders: null, [Symbol(resource_symbol)]: [HTTPServerAsyncResource] }, on: [Function: socketListenerWrap], addListener: [Function: socketListenerWrap], prependListener: [Function: socketListenerWrap], setEncoding: [Function: socketSetEncoding], _paused: false, _httpMessage: ServerResponse { _events: [Object: null prototype], _eventsCount: 1, _maxListeners: undefined, outputData: [], outputSize: 0, writable: true, destroyed: false, _last: false, chunkedEncoding: false, shouldKeepAlive: true, maxRequestsOnConnectionReached: false, _defaultKeepAlive: true, useChunkedEncodingByDefault: true, sendDate: true, _removedConnection: false, _removedContLen: false, _removedTE: false, strictContentLength: false, _contentLength: null, _hasBody: true, _trailer: '', finished: false, _headerSent: false, _closed: false, socket: [Circular *1], _header: null, _keepAliveTimeout: 5000, _onPendingData: [Function: bound updateOutgoingData], req: [Circular *2], _sent100: false, _expect_continue: false, _maxRequestsPerSocket: 0, [Symbol(shapeMode)]: false, [Symbol(kCapture)]: false, [Symbol(kBytesWritten)]: 0, [Symbol(kNeedDrain)]: false, [Symbol(corked)]: 0, [Symbol(kOutHeaders)]: [Object: null prototype], [Symbol(errored)]: null, [Symbol(kHighWaterMark)]: 16384, [Symbol(kRejectNonStandardBodyWrites)]: false, [Symbol(kUniqueHeaders)]: null }, [Symbol(async_id_symbol)]: 250, [Symbol(kHandle)]: TCP { reading: true, onconnection: null, _consumed: true, [Symbol(owner_symbol)]: [Circular *1] }, [Symbol(lastWriteQueueSize)]: 0, [Symbol(timeout)]: null, [Symbol(kBuffer)]: null, [Symbol(kBufferCb)]: null, [Symbol(kBufferGen)]: null, [Symbol(shapeMode)]: true, [Symbol(kCapture)]: false, [Symbol(kSetNoDelay)]: true, [Symbol(kSetKeepAlive)]: false, [Symbol(kSetKeepAliveInitialDelay)]: 0, [Symbol(kBytesRead)]: 0, [Symbol(kBytesWritten)]: 0 }, _consuming: false, _dumped: false, [Symbol(shapeMode)]: true, [Symbol(kCapture)]: false, [Symbol(kHeaders)]: { host: 'localhost:8888', connection: 'keep-alive', 'content-length': '45', 'sec-ch-ua-platform': '"Windows"', 'user-agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/135.0.0.0 Safari/537.36', accept: 'application/json, text/plain, */*', 'sec-ch-ua': '"Google Chrome";v="135", "Not-A.Brand";v="8", "Chromium";v="135"', 'content-type': 'application/json', 'x-custom-header': 'foobar', 'sec-ch-ua-mobile': '?0', origin: 'http://localhost:5173', 'sec-fetch-site': 'same-site', 'sec-fetch-mode': 'cors', 'sec-fetch-dest': 'empty', referer: 'http://localhost:5173/', 'accept-encoding': 'gzip, deflate, br, zstd', 'accept-language': 'zh-CN,zh;q=0.9' }, [Symbol(kHeadersCount)]: 34, [Symbol(kTrailers)]: null, [Symbol(kTrailersCount)]: 0 }

原生node.js接收前端数据

//接收数据 let body = ''; // 每次接收到一部分数据，就累加到 body req.on('data', chunk => { body += chunk.toString(); }); // 数据接收完毕后，在这里处理完整的 body req.on('end', () => { //解析JSON格式 try { const data = JSON.parse(body); console.log('接收到的数据：', data); res.end('ok'); } catch (err) { console.error('解析失败：', err); res.statusCode = 400; res.end('Invalid JSON'); } });

req.on

在 Node.js 的 HTTP 服务器处理中，`req.on` 用于监听 HTTP 请求对象 (`IncomingMessage`) 的事件。`req` 是一个继承了 `EventEmitter` 类的对象，可以通过 `.on()` 方法监听各种请求相关的事件。 以下是常见的 `req.on` 使用场景和详细解释： --- ### 1. **接收请求体数据（POST/PUT 等）** 当客户端通过 POST 或 PUT 方法发送数据时，数据会被分成多个 **chunk（数据块）** 传输。你需要监听 `'data'` 和 `'end'` 事件来完整接收数据。 ```javascript const http = require('http'); const server = http.createServer((req, res) => { let body = []; // 监听 'data' 事件：每次接收到数据块时触发 req.on('data', (chunk) => { body.push(chunk); // 将数据块存入数组 }); // 监听 'end' 事件：所有数据接收完成后触发 req.on('end', () => { body = Buffer.concat(body).toString(); // 合并所有数据块 console.log('Received body:', body); res.end('Data received'); }); }); server.listen(3000); ``` - **为什么需要这样处理？** HTTP 请求体可能很大，Node.js 以流（Stream）的形式逐步传输数据，避免内存溢出。 --- ### 2. **处理请求错误** 监听 `'error'` 事件可以捕获请求过程中发生的错误（如客户端提前断开连接）。 ```javascript req.on('error', (err) => { console.error('Request error:', err); // 可以在此处关闭连接或清理资源 }); ``` --- ### 3. **其他事件** - **`'close'`**: 当底层连接关闭时触发。 - **`'aborted'`**: 当请求被客户端中止时触发。 --- ### 4. **注意事项** - **必须监听 `'data'` 才会触发 `'end'`** 如果你不监听 `'data'` 事件，流会处于 **暂停模式**，`'end'` 事件永远不会触发。 - **流（Stream）的工作模式** - **流动模式（Flowing Mode）**: 通过 `.on('data')` 自动接收数据。 - **暂停模式（Paused Mode）**: 需要手动调用 `.read()` 读取数据。 - **框架的封装** 在 Express 或 Koa 等框架中，通常使用中间件（如 `body-parser`）自动处理请求体数据，无需手动监听 `'data'` 和 `'end'`。 --- ### 5. **完整示例** ```javascript const http = require('http'); const server = http.createServer((req, res) => { let data = ''; req.on('data', (chunk) => { data += chunk; // 拼接数据块（字符串形式） }); req.on('end', () => { try { const jsonData = JSON.parse(data); // 解析 JSON 数据 res.end('Data processed'); } catch (err) { res.statusCode = 400; res.end('Invalid JSON'); } }); req.on('error', (err) => { console.error('Request error:', err); res.statusCode = 500; res.end('Internal Server Error'); }); }); server.listen(3000, () => { console.log('Server running on port 3000'); }); ``` --- ### 6. **Express 中的对比** 在 Express 中，使用 `express.json()` 中间件后，可以直接通过 `req.body` 获取解析后的数据，无需手动监听事件： ```javascript const express = require('express'); const app = express(); app.use(express.json()); // 自动处理 JSON 请求体 app.post('/', (req, res) => { console.log(req.body); // 直接访问解析后的数据 res.send('Data received'); }); app.listen(3000); ``` --- ### 总结 - **`req.on`** 用于监听 HTTP 请求对象的事件，适用于原始 Node.js 环境。 - 主要事件：`data`（接收数据块）、`end`（数据接收完成）、`error`（处理错误）。 - 在框架中（如 Express），通常有更简洁的封装，无需直接操作这些事件。