1.功能：node.js中的字符
2.核心的方法：
1.parse：将字符转变为对象<!--parse有三个参数--><!--parse（str，arg1，arg）str：你要处理的字符arg1:分隔字符arg2：将“=”转化为“：”，（但前提是&符号是被提前转化的）-->例：var qs = require('querystring')var url = require('url')var str = 'http://www.baidu.com:8080/001?a=1&b=2#hash=20'var obj = qs.parse(str, '?', '&')// console.log('====================================');//console.log(obj); cx// console.log('====================================');/* { 'http://www.baidu.com:8080/001?a': '1',b: '2#hash=20' } */2.stringify：将对象转变为字符 // stringify// console.log( qs.stringify( obj ) )// var str = 'http://www.baidu.com:8080/001?a=1&b=2#hash=20'// http%3A%2F%2Fwww.baidu.com%3A8080%2F001=&a%3D1=b%3D2%23hash%3D20// %3A : %2F / %3D = %23 # =& ?3.escape：将中文字编码// escape var charaStr = 'http://www.baidu.com/001?city=北京'var urlObj = url.parse(charaStr)var query = urlObj.query // city = 北京// console.log( qs.escape( query) )//city%3D%E5%8C%97%E4%BA%AC4.unescape：将中文字符解码小爬虫： 使用数据请求一段内容，然后将这段内容数据清洗，最后在通过后端服务器发送到前台页面
步骤
1.数据请求，获得数据
2.数据清洗（工具 cheerio）
3.安装 cheerio $ cnpm i cheerio -s
4.使用cheerio
5.发送前台
例
请求的网址： http://jx.1000phone.net/teacher.php/Class/classDetail/param/rqiWlsefmajGmqJhXXWhl3ZiY2dn
var http = require( 'http' )var cheerio = require( 'cheerio' )// http.get(url/options,callback)const options = { hostname: 'jx.1000phone.net',port: 80, path: '/teacher.php/Class/classDetail/param/rqiWlsefmajGmqJhXXWhl3ZiY2dn',method: 'get', headers: { 'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3','Accept-Encoding': 'gzip, deflate','Accept-Language': 'zh-CN,zh;q=0.9,en-US;q=0.8,en;q=0.7','Cache-Control': 'no-cache','Cookie': 'PHPSESSID=ST-46480-wNTDM48QXeWJfh--WJ-Oupg44Oo-izm5ejd5j1npj2pjc7i3v4z','Host': 'jx.1000phone.net','Pragma': 'no-cache','Proxy-Connection': 'keep-alive','Referer': 'http://jx.1000phone.net/teacher.php/Class/index','Upgrade-Insecure-Requests': '1','User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.131 Safari/537.36','Content-Type': 'application/x-www-form-urlencoded' }};// 创建静态服务器http.createServer( function ( request, response ) {response.writeHead( 200 , {'Content-type': 'text/html;charset=utf8' })var req = http.get( options,function( res ) {res.setEncoding('utf8');let rawData = '';res.on('data', (chunk) => { rawData += chunk; });res.on('end', () => { try { var $ = cheerio.load( rawData ) $('td.student a').each( function( index,ele ) { response.write( `<h3>${$( this ).text().toString()}</h3>` ) }) response.end() } catch (e) { console.error(e.message); }})}).on('error', (e) => { // get的报错console.error(`problem with request: ${e.message}`);}) req.end()}).listen(8000,'localhost',function () {console.log( `服务器运行在： http://localhost:8000` )})例：
var Events = require('events') class MyEvents extends Events {}var myEvents = new MyEvents ()// console.log( myEvents )// 声明事件myEvents.on('aa',function(){console.log( 'hello Node.js' )})// 事件的触发myEvents.emit('aa')fs:是Node.js中文件系统
功能：操作文件或者是目录
文件：
增：writeFile（路径，内容，错误优先回调）例：增:（创建）var fs = require( 'fs' ) fs.writeFile('./dist/1.txt','hello yyb',function( error ) { if( error ) throw error 删:unlinkvar fs = require( 'fs' )fs.unlink( './dist/1.txt', function( error ) {if( error ) throw error console.log( '文件删除成功' ) }) 改：appendFile var fs = require( 'fs' ) fs.appendFile('./dist/1.txt','\nhello 千锋~~~','utf8',function( error ) { if( error ) throw error console.log('文件修改成功') }) 查：readFile var fs = require( 'fs' ) fs.readFile( './dist/1.txt','utf8',function( error, data ) { if ( error ) throw error console.log( data.toString() ) //二进制数据 console.log( data ) console.log('文件读成功了')})目录的增删改查：目录-增：mkdirvar fs = require( 'fs' )fs.mkdir('./dist',function( error ) { if( error ) throw error console.log( '目录创建成功' ) }) 目录-删：rmdirvar fs = require( 'fs' )fs.rmdir(path,callback) //这个方法只能删除空目录 fs.rmdir( './fs_dist', function ( error ) { if( error ) throw error console.log('目录删除成功') }) // fs.readdir('./fs_dist','utf-8',function ( error,data ) {// if( error ) throw error // //console.log( data ) // 以文件名为元素构成的数组// for ( var i = 0 ; i < data.length; i ++ ){// fs.unlink( `./fs_dist/${data[i]}`,function( error ) {// if( error ) throw error // })// }// })fs.rmdir('./fs_dist',function( error ) { if( error ) throw error }) 目录-改：renamevar fs = require( 'fs' )fs.rename('./dist','./fs_dist',function( error ) { if( error ) throw error console.log(' 目录名称修改成功 ')})目录-查：readdirvar fs = require( 'fs' )for( var i = 0 ; i < 10 ; i ++ ){fs.writeFile(`./fs_dist/${i}.txt`,i,function( err ) { console.log( `第${i}个文件创建成功` ) }) }fs.readdir('./fs_dist','utf-8',function ( error,data ) { if( error ) throw error console.log( data ) // 以文件名为元素构成的数组 for ( var i = 0 ; i < data.length; i ++ ){ fs.readFile( `./fs_dist/${data[i]}`,'utf8',function( error , content ) { if( error ) throw error console.log( content ) }) } })流：减少内存消耗，增加效率
可读的流；可写的流
例：压缩包创建
var fs = require( ‘fs‘ )
var zlib = require(‘zlib‘) // 创建压缩包
var readeStream = fs.createReadStream( ‘./dist/1.txt‘ )
var writeStream = fs.createWriteStream( ‘./dist/1.txt.gz‘ )
var gzip = zlib.createGzip() // 空压缩包
readeStream
.pipe( gzip )
.pipe( writeStream )
名词：pipe-->管道流
什么是路由：
是指分组从源到目的地时，决定端到端路径的网络范围的进程
var http = require( 'http' )var fs = require( 'fs' )http.createServer( function ( req, res ) { switch ( req.url ) { case '/home': res.write('home') res.end() break; case '/mine': res.write('mine') res.end() break; case '/login': fs.readFile( './static/login.html',function ( error , data ) { if ( error ) throw error res.write( data ) res.end() }) break; case '/fulian.jpg': fs.readFile( './static/fulian.jpg','binary',function( error , data ) { if( error ) throw error res.write( data, 'binary' ) res.end() }) break; default: break; }}).listen( 8000, 'localhost', function () { console.log( '服务器运行在： http://localhost:8000' )})function* p1 () { yield '任务1'; yield '任务2'; yield '任务3'; yield '任务4'; yield '任务5'; yield function* p2() { yield '任务7' } return '任务6'}var p = p1()console.log(p.next()) //{ value: '任务1', done: false }console.log(p.next()) //{ value: '任务2', done: false }...... const p1 = new Promise ( function ( resolve, reject ) { resolve( '任务一' ) }) .then ( function ( data ) { console.log( data ) }) const p2 = new Promise ( function ( resolve, reject ) { setTimeout( function () { resolve( '任务二' ) },1000) }) .then ( function ( data ) { console.log( data ) }) console.log( '主线程任务 ') // Promise // .all([p1,p2]) // 先执行all中所有任务， 执行完成之后再去执行后面的任务 // .then( data => { // console.log( '任务3' ) // }) Promise .race([p1,p2]) // race 谁快输出谁 .then( data => { console.log( '任务3' ) })
