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多人協作或者是需要引入大量的js時很容易出現變量被覆蓋，方法被重寫，特別是存在依賴關系時，很容易導致出錯，模塊管理機制就很好的避免了這一問題，Commonjs規范，Node.js借鑒了其規范

命令行輸入node進入node執行環境，可執行javascript,如

var a = 1; var b = 2; var add = function(a,b){return a + b;};

add(a,b);

會得到執行結果為3；

谷歌瀏覽器f12點console輸入也可執行，兩者是執行環境的不同，瀏覽器的全局變量為window,node的全局變量為process

進入項目目錄 cd XXX

ls 查看當前目錄

node XX.js 執行XX.js里寫的目錄命令

以下基于v10.15.0書寫

var http = require('http');

http.createServer(function(req,res){

res.statusCode = 200;

res.setHeader('Content-Type','text/plain');

res.end('Hello! Node.js')

}).listen(3000,'127.0.0.1',function(){

console.log("啟動完畢");

})

console.log("server run!")

執行結果??server run!? ?啟動完畢? 說明為非阻塞執行

改變js命令后需要重新啟動服務刷新頁面生效

此寫法為鏈式調用 可以拆開 var server = http.creatServer..... ;? server.listen(...

工具 git bash?

https://www.git-scm.com/downloads

官網安裝node

可用git bash 或者開始菜單輸入cmd啟動系統自帶命令行通過查看版本號看是否安裝成功?

node -v? ? ?npm -v

輸入 node 回車進入node環境 可執行命令如1+2 ,ctrl+c 退出環境

學習參考網站：

1. https://nodejs.org/en/?官網 了解更新等

2. https://www.npmjs.com/?項目初始可以來找包看架構

3. https://github.com/? 閱讀優秀的源碼是快速提高的方法

4. https://stackoverflow.com/?技術問答社區

node的全局變量是：process

使用n模塊管理node版本，n+版本號，安裝版本，在已安裝的版本中上下鍵切換

var https = require('https')

var querystring = require('querystring')

var postData = querystring.stringify({

'content': '覺得老師講課風格很幽默',

'cid': '348'

})

var options = {

host: 'www.xianlaiwan.cn',

port: 443,

path: '/course/docomment',

methods: "POST",

headers: {

"Accept": "application/json, text/javascript, */*; q=0.01",

"Accept-Encoding": "gzip, deflate, br",

"Accept-Language": "zh-CN,zh;q=0.9,en;q=0.8",

"Connection": "keep-alive",

"Content-Length": postData.length,

"Content-Type": "application/x-www-form-urlencoded; charset=UTF-8",

"Cookie": "imooc_uuid=24c9737a-e062-45a5-adba-abcdee6cdac9; imooc_isnew_ct=1540445186; imooc_isnew=2; zg_did=%7B%22did%22%3A%20%22166e6b1e449cf2-0cb6c25626a0b3-594d2a16-1fa400-166e6b1e44bca9%22%7D; Hm_lvt_fb538fdd5bd62072b6a984ddbc658a16=1540445186,1540452644,1541410617,1541570612; loginstate=1; apsid=Q4MmZjNjY5NDMxNWZiNDgwNmU0MTgxYWI0ZGYyZWUAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAMzY4NjI2NAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAxMDQ5MTk0NjA4QHFxLmNvbQAAAAAAAAAAAAAAAAAAADllN2I0NjhjY2E3OGU4MjYxY2FiODcxNWVmZGVlNzdjvhEPXGtV01k%3DY2; PHPSESSID=igfbk13je3di0qcn82oa9n5f65; Hm_lvt_f0cfcccd7b1393990c78efdeebff3968=1544166148,1544434856,1545014246,1545613505; cninfo=syb20-e1b10d50f61d93b98befa04edc7c22a5; IMCDNS=0; userId=15458167777966; zg_f375fe2f71e542a4b890d9a620f9fb32=%7B%22sid%22%3A%201545896243734%2C%22updated%22%3A%201545896243830%2C%22info%22%3A%201545619079648%2C%22superProperty%22%3A%20%22%7B%5C%22%E5%BA%94%E7%94%A8%E5%90%8D%E7%A7%B0%5C%22%3A%20%5C%22%E6%85%95%E8%AF%BE%E7%BD%91%E6%95%B0%E6%8D%AE%E7%BB%9F%E8%AE%A1%5C%22%2C%5C%22%E5%B9%B3%E5%8F%B0%5C%22%3A%20%5C%22web%5C%22%7D%22%2C%22platform%22%3A%20%22%7B%7D%22%2C%22utm%22%3A%20%22%7B%7D%22%2C%22referrerDomain%22%3A%20%22www.xianlaiwan.cn%22%2C%22cuid%22%3A%20%22POesjyNXSEI%2C%22%2C%22zs%22%3A%200%2C%22sc%22%3A%200%7D; Hm_lpvt_f0cfcccd7b1393990c78efdeebff3968=1545896244; cvde=5c2030bcbf744-362",

"Host": "www.xianlaiwan.cn",

"Origin": "http://www.xianlaiwan.cn",

"Referer": "http://www.xianlaiwan.cn/video/8837",

"User-Agent": " Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.67 Safari/537.36",

"X-Requested-With": "XMLHttpRequest"

}

}

var req = https.request(options, function (res) {

console.log('Status:' + res.statusCode)

console.log('Headers:' + JSON.stringify(res.headers))

// 接收數據的時候,node 以流的形式發送，會觸發data事件

res.on('data', function (chunk) {

console.log(Buffer.isBuffer(chunk))

console.log(typeof chunk)

})

res.on('end', function () {

console.log("評論完畢")

})

})

req.on('error', function (e) {

console.log("Error:" + e.message)

})

req.write(postData)

req.end()

var EventEmitter = require('events').EventEmitter

var life = new EventEmitter()

life.on('買禮物', function (who) {

console.log('買禮物1' + who + '005')

})

life.on('買禮物', function (who) {

console.log('買禮物2' + who + '005')

})

life.on('買禮物', function (who) {

console.log('買禮物3' + who + '001')

})

life.on('買禮物', function (who) {

console.log('買禮物4' + who + '002')

})

life.on('買禮物', function (who) {

console.log('買禮物5' + who + '003')

})

life.on('買禮物', function (who) {

console.log('買禮物6' + who + '004')

})

life.on('買禮物', function (who) {

console.log('買禮物7' + who + '005')

})

life.on('買禮物', function (who) {

console.log('買禮物8' + who + '006')

})

life.on('買禮物', function (who) {

console.log('買禮物9' + who + '007')

})

life.on('買禮物', function (who) {

console.log('買禮物10' + who + '008')

})

life.on('買禮物', function (who) {

console.log('買禮物11' + who + '009')

})

life.on('買禮物', function (who) {

console.log('買禮物12' + who + '010')

})

// life.removeAllListeners()

life.emit('買禮物', '給~')

// var http = require('http')

var https = require('https')

var cheerio = require('cheerio')

var url = 'http://www.xianlaiwan.cn/learn/348'

function filterChapters(html) {

var $ = cheerio.load(html)

var chapters = $('.chapter')

// [{

// ? ? chapterTitle: '',

// ? ? videos: [

// ? ? ? ? title: '',

// ? ? ? ? id: ''

// ? ? ]

// }]

var courseData = []

chapters.each(function (item) {

var chapter = $(this)

var chapterTitle = chapter.find('.chapter-description').text()

var videos = chapter.find('.video').children('li')

var chapterData = {

chapterTitle: chapterTitle,

videos: []

}

videos.each(function (item) {

var video = $(this).find('.J-media-item')

var videoTitle = video.text()

var id = video.attr('href').split('video/')[1]

chapterData.videos.push({

title: videoTitle,

id: id

})

})

courseData.push(chapterData)

})

return courseData

}

function printCourseInfo(courseData) {

courseData.forEach(item => {

var chapterTitle = item.chapterTitle

console.log(chapterTitle + '\n')

item.videos.forEach(video => {

console.log('【' + video.id + '】' + video.title + '\n')

})

});

}

https.get(url, function (res) {

var html = ''

res.on('data', function (data) {

html += data

})

res.on('end', function () {

var courseData = filterChapters(html)

printCourseInfo(courseData)

})

}).on('error', function () {

console.log('獲取出錯')

})

function printCourseInfo(courseData){

courseData.forEach(function(item){

var chapterTitle = item.chapterTitle;

console.log(chapterTitle+"\n");

item.videos.forEach(function(video){

????console.log("["+video.id+"] "+ video.title +"\n");

})

})

}

上下文常常代表this變量的值

第一種情況：this==調用這個函數的對象

var pet = {

????words:"...",

????speak:function(){

????console.log(this.words)

????console.log(this === pet)//這里表示this就是pet對象

????}

}

pet.speak();

第二種情況：this指向global；

function pet(words){

????this.word = words;

console.log(this.word);

console.log(this)//這里this指向全局global相當于頁面中的window

}

pet("...")

兩種調用方法打印的this.words是一樣的，但是this卻指向不同的地方。

第三種情況：this指向新new的對象

function pet（words){

this.words = words;

this.speak = function(){

????console.log(this.words);

console.log(this === cat)//指向新構建的對象cat

}

}

var cat = new per("miao")

cat.speak();

：：：：

this關鍵字指向函數的擁有者&this關鍵字只能在函數內部使用

-----------

使用call和apply可以改變上下文執行對象

var pet = {

words:"...",

speak:function(say){

????console.log(say+" " +this.words);

}

}

pet.speak("speak")

var dog = {

words:"wang"

}

pet.speak.call(dog,"sepak");//制定dog對象為pet的上下文（this）

利用call_apply改變上下文的方法來實現繼承

function Pet(words){

this.words = words;

this.speak = function(){

console.log(this.words);

}

}

function Dog(words){

Pet.call(this,words);

//Pet.apply(this,arguments);

}

var dog = new Dog("Wang");

dog.speak();

//dog同歸call、apply修改上下文實現繼承Pet（）的屬性和方法

11111111

利用call實現繼承

function Pet(words){

? ? this.words = words

? ? this.speak = function(){

? ? ? ? console.log(this.words)

? ? }

}

function Dog(words){

? ? Pet.call(this,words)

}

var dog = new Dog('wang')

dog.speak()

調用pet的speak方法，this指針指向了pet對象(pet對象有speak方法),通過call改變了執行上下文，pet.speak的指針就指向了dog