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')