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

 1 const http = require('http')
 2 
 3 const port = 8080
 4 const hostname = 'localhost'
 5 
 6 const server = http.createServer((request, response)=>{
 7   response.writeHead(200, {'Content-Type': 'application/html'})
 8   response.write('<b>hellow</b>')   
 9   response.end()
10 })
11 
12 server.listen(port, hostname, ()=>{
13   console.log(`server runing at http://${hostname}:${port}`)
14 })

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https.request()

get:

 1 const https = require('https')
 2 
 3 const options = {
 4   hostname: 'api.douban.com',
 5   port: 443,
 6   method: 'GET',
 7   path: '/v2/movie/in_theaters'
 8 }
 9 
10 let responseData = ''
11 
12 const request = https.request(options, (response)=>{
13   // 后端返回的数据编码，默认为buffer
14   response.setEncoding('utf8')
15 
16   // 接收后端的数据流，后端的数据会成批量返回
17   // 通过data事件监听，来收取数据
18   response.on('data', (chunk)=>{
19     responseData += chunk
20   })
21 
22   // 数据接受完毕的事件
23   response.on('end', ()=>{
24     JSON.parse(responseData).subjects.map((item)=>{
25       console.log(item.title);
26     })
27   })
28 })
29 
30 request.end()

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post:

 1 var http = require('http')
 2 var querystring = require('querystring')
 3 
 4 var postData = querystring.stringify({
 5   /** .... **/
 6 })
 7 
 8 var options = {
 9   hostname: 'www.baidu.com',
10   port: 80,
11   method: 'POST',
12   path: '/ajax/...',
13   headers: {
14       /** .......  **/
15     'Content-Length': postData.length,
16     /**.....**/
17   }
18 }
19 
20 var request = http.request(options, (res) => {
21   console.log('Status:' + res.statusCode);
22 })
23 
24 request.on('err', (error) => {
25   console.log(error);
26 })
27 
28 request.write(postData)
29 
30 request.end()

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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

 1 const https = require('https')
 2 const cheerio = require('cheerio')
 3 
 4 options = {
 5   hostname: 'www.jd.com',
 6   port: 443,
 7   method: 'GET',
 8   path: '/'
 9 }
10 
11 let responseData = ''
12 
13 function filterData(data) {
14   let $ = cheerio.load(data)
15   let a = $('.cate_menu_item').find('a')
16   a.each((index, value)=>{
17     console.log($(value).text());
18   })
19 }
20 
21 const request = https.request(options, (response)=>{
22   response.setEncoding = 'utf8'
23   response.on('data', (chunk)=>{
24     responseData += chunk
25   })
26   response.on('end', ()=>{
27     filterData(responseData)
28   })
29 })
30 
31 request.end()

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events 事件

 1 const EventEmitter = require('events')
 2 
 3 class Player extends EventEmitter {}
 4 
 5 let player = new Player()
 6 
 7 player.once('play', (track)=>{
 8   console.log(`正在直播${track}`);
 9 })
10 
11 player.emit('play', '精绝古城')
12 player.emit('play', '黄皮子坟')

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