nodeJs 常用模块（一）

 url

url.parse()

querystring

querystring.parse( [string] , [分隔符] )  ，解析为js字面量

querystring.stringify() ，将js对象转为字符串

querystring.escape() ，转译

 

实际上浏览器上也有类似功能

querystring.unscape() ,反转译

http：

 开启一个web服务器

const http = require('http')

const port = 8080
const hostname = 'localhost'

const server = http.createServer((request, response)=>{
  response.writeHead(200, {'Content-Type': 'application/html'})
  response.write('<b>hellow</b>')   
  response.end()
})

server.listen(port, hostname, ()=>{
  console.log(`server runing at http://${hostname}:${port}`)
})

https.request()

 get:

const https = require('https')

const options = {
  hostname: 'api.douban.com',
  port: 443,
  method: 'GET',
  path: '/v2/movie/in_theaters'
}

let responseData = ''

const request = https.request(options, (response)=>{
  // 后端返回的数据编码，默认为buffer
  response.setEncoding('utf8')

  // 接收后端的数据流，后端的数据会成批量返回
  // 通过data事件监听，来收取数据
  response.on('data', (chunk)=>{
    responseData += chunk
  })

  // 数据接受完毕的事件
  response.on('end', ()=>{
    JSON.parse(responseData).subjects.map((item)=>{
      console.log(item.title);
    })
  })
})

request.end()

post:

var http = require('http')
var querystring = require('querystring')

var postData = querystring.stringify({
  /** .... **/
})

var options = {
  hostname: 'www.baidu.com',
  port: 80,
  method: 'POST',
  path: '/ajax/...',
  headers: {
      /** .......  **/
    'Content-Length': postData.length,
    /**.....**/
  }
}

var request = http.request(options, (res) => {
  console.log('Status:' + res.statusCode);
})

request.on('err', (error) => {
  console.log(error);
})

request.write(postData)

request.end()

简单爬虫spire：

node后端解析网页工具：cheerio，其语法与jQuery一致

npm i cheerio -D

const https = require('https')
const cheerio = require('cheerio')

options = {
  hostname: 'www.jd.com',
  port: 443,
  method: 'GET',
  path: '/'
}

let responseData = ''

function filterData(data) {
  let $ = cheerio.load(data)
  let a = $('.cate_menu_item').find('a')
  a.each((index, value)=>{
    console.log($(value).text());
  })
}

const request = https.request(options, (response)=>{
  response.setEncoding = 'utf8'
  response.on('data', (chunk)=>{
    responseData += chunk
  })
  response.on('end', ()=>{
    filterData(responseData)
  })
})

request.end()

events 事件 

const EventEmitter = require('events')

class Player extends EventEmitter {}

let player = new Player()

player.once('play', (track)=>{
  console.log(`正在直播${track}`);
})

player.emit('play', '精绝古城')
player.emit('play', '黄皮子坟')