重学Node 0x1 Node Modules System（2）_node thermal state 0x1e-优快云博客

本文链接：https://blog.youkuaiyun.com/funkstill/article/details/104168037

本文深入探讨了Node.js中关键的内置模块，包括Path、OS、FileSystem、Events和HTTP模块的使用方法及示例。从文件路径解析到操作系统信息获取，从文件系统操作到事件驱动机制，再到HTTP服务器创建，全面覆盖了Node.js开发的基础知识点。

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Path Module

// app.js
const path = require('path')
const pathObj = path.parse(__filename)
console.log(pathObj)

OS Module

// app.js
const os = require('os')

const totalMemory = os.totalmem()
const freeMemory = os.freemem()
const userInfo = os.userInfo()

console.log(`totalMemory:${totalMemory}`)
console.log(`freeMemory:${freeMemory}`)
console.log(userInfo)

File System Module

// app.js
const fs = require('fs')

// const files = fs.readdirSync('./')
// console.log(files)

fs.readdir('./', (err, files) => {
  if (err) console.log('ERR', err)
  else console.log('Result', files)
})

Events Module

// app.js
const EventEmitter = require('events')
const emitter = new EventEmitter()

// Register a listener
// emitter.addListener()
emitter.on('messageLogged', function() {
  console.log('Listener called')
})
// Raise an event 
emitter.emit('messageLogged')

Event Arguments

// app.js
const EventEmitter = require('events')
const emitter = new EventEmitter()

// Register a listener
// emitter.addListener()
emitter.on('messageLogged', function(arg) {
  console.log('Listener called', arg)
})
// Raise an event 
emitter.emit('messageLogged', { id: 1, url: 'http://' })

Extending Eventmitter

//logger.js
const EventEmitter = require('events')

const url = 'http://mylogger.io/log'
class Logger extends EventEmitter {
  log(message) {
    // send an HTTP request
    console.log(message)
    // Raise an event 
    this.emit('messageLogged', { id: 1, url: 'http://' })
  }
}

module.exports = Logger

// app.js
const EventEmitter = require('events')

const Logger = require('./logger')
const logger = new Logger()
// Register a listener
// emitter.addListener()
logger.on('messageLogged', function(arg) {
  console.log('Listener called', arg)
})
logger.log('message')

HTTP Module

// app.js
const http = require('http')

const server = http.createServer()

server.on('connection', (socket) => {
  console.log('New connection...')
})

server.listen(3000)

console.log('Listening on port 3000...')

// app.js
const http = require('http')

const server = http.createServer((req, res) => {
  if (req.url === '/') {
    res.write('hello world')
    res.end()
  }
})

server.listen(3000)

console.log('Listening on port 3000...')

more routers

// app.js
const http = require('http')

const server = http.createServer((req, res) => {
  if (req.url === '/') {
    res.write('hello world')
    res.end()
  }
  if (req.url === '/api/courses') {
    res.write(JSON.stringify([1,2,3]))
    res.end()
  }
})

server.listen(3000)

console.log('Listening on port 3000...')