node

Posted 2020-10-07 Simon1020

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nodejs.org

https://www.npmjs.com/

https://github.com/

https://stackoverflow.com/

https://www.liaoxuefeng.com/wiki/001434446689867b27157e896e74d51a89c25cc8b43bdb3000

Sublime Text 3
webstorm

http://nodejs.cn/api/
http://www.runoob.com/angularjs/angularjs-tutorial.html

1.安装 Node.js　　0.10.3x为例

win:略

linux(源码编译安装):

mac:

更新:

上下键切换

nodejs的模块与commonsj规范

https://nodejs.org/docs/latest-v0.10.x/api/

http

http://fex.baidu.com/blog/2014/05/what-happen/

chrome://net-internals/#dns

以下转自: http://www.cnblogs.com/haoyijing/p/6478742.html

nodejs学习(imooc课程笔记, 主讲人Scott)

课程地址:

进击Node.js基础（一）

进击Node.js基础（二）

1. nodejs创建服务器

var http = require(\'http\');        //加载http模块

//请求进来时, 告诉服务器做什么, 于是给createServer传递一个匿名回调函数. 
//两个参数, 前面是请求体, 后面是响应体. 请求体用来获取请求相应信息,比如请求ip地址,请求的类型get/post,res用来返回响应
http.createServer(function(req, res) {
    res.writeHead(200, {\'Content-Type\': \'text/palin\'});
    res.end(\'Hello World\\n\');
}).listen(1337, \'127.0.0.1\');        //通过listen使服务器在1337端口监听请求
console.log(\'Server running at https://127.0.0.1:1337/\');

2. nodejs安装:

一开始直接使用sudo apt-get install node后, 安装好的node不能启动且node -v也没有输出. node.js的版本号是v0.10.25.但是用npm安装一些包时候却说node版本不够, 没搞明白node和nodejs区别在哪里.

于是卸载掉从nodejs.org上下了新版, 是node v6.10.0. 解压后, 直接在那个目录下可以启动node, 在网上查了使用了一个链接, 分别把node 和 npm设置了全局:

sudo ln -s /media/hao/3b6b3418-c087-4836-a75d-6d7a6023e495/Programs/node-v6.10.0-linux-x64/bin/node /usr/sbin/node
sudo ln -s /media/hao/3b6b3418-c087-4836-a75d-6d7a6023e495/Programs/node-v6.10.0-linux-x64/bin/npm /usr/sbin/npm

可以用了.

关于nodejs和node版本的区别,参考这个帖子吧: nodejs各版本的区别

3. 模块: 从这里开始都是慕课网老师Scott进击NodeJS基础(一)(二)课程的笔记

创建模块
```
teacher.js
```
导出模块
```
exports.add = function(){ }
```
加载模块
```
var teacher = require(\'./teacher.js\')
```
使用模块
```
teacher.add(\'Scott\')
```

4. nodejs中一些api

url:
1. url.parse
2. url.format:
3. url.resolve
querystring

5. 用nodejs做的一个爬虫:

var http = require(\'http\')
var cheerio = require(\'cheerio\')        //npm install cheerio
var url = \'http://www.imooc.com/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(\'strong\').text().trim(\'\\n\').split(\'\\n\')[0]
        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().split(/\\s+/).slice(1,-2).join(\' \')
            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(function(item){
        var chapterTitle = item.chapterTitle
        console.log(chapterTitle + \'\\n\')

        item.videos.forEach(function(video){
            console.log(\'   [\' + video.id + \']\' + video.title + \'\\n\')
        })
    })
}
http.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(\'获取课程数据错误\')
})

6. 事件监听的一个小例子

var EventEmitter = require(\'events\').EventEmitter
var life = new EventEmitter()

//addEventListener

life.setMaxListeners(6)     //设置事件最大监听数 默认为10. 超出这个数目会报警告

life.on(\'求安慰\', function(who){
    console.log(\'给 \' + who + \' 倒水\')
})

life.on(\'求安慰\', function(who){
    console.log(\'给 \' + who + \' ...1\')
})

life.on(\'求安慰\', function(who){
    console.log(\'给 \' + who + \' ...2\')
})

life.on(\'求安慰\', function(who){
    console.log(\'给 \' + who + \' ...3\')
})

life.on(\'求安慰\', function(who){
    console.log(\'给 \' + who + \' ...4\')
})

life.on(\'求安慰\', function(who){
    console.log(\'给 \' + who + \' ...5\')
})

life.on(\'求安慰\', function(who){
    console.log(\'给 \' + who + \' ...6\')
})


var hasBeenListener = life.emit(\'求安慰\', \'杠子\')      //会返回值, 看是否被监听过

//要移除函数, 不能够使用匿名函数, 只能移除具名函数

console.log(life.listeners(\'求安慰\').length)   //查询监听事件数
console.log(EventEmitter.listenerCount(life, \'求安慰\'))

life.removeAllListeners(\'求安慰\')
life.emit(\'求安慰\',\'gangzi\')

7. Promise.js imooc

<!DOCTYPE html>
<html>
<head>
    <title>Promise animation</title>
    <style type="text/css">
        .ball{
            width: 40px;
            height: 40px;
            border-radius: 20px;
        }
        .ball1 { background: red;}
        .ball2 { background: yellow;}
        .ball3 { background: green;}
    </style>
    <script type="text/javascript" src="/home/hao/node_modules/bluebird/js/browser/bluebird.js"></script>
</head>

<body>
    <div class="ball ball1" style="margin-left: 0;"></div>
    <div class="ball ball2" style="margin-left: 0;"></div>
    <div class="ball ball3" style="margin-left: 0;"></div>
    

</body>
<script type="text/javascript">
    var ball1 = document.querySelector(\'.ball1\')
    var ball2 = document.querySelector(\'.ball2\')
    var ball3 = document.querySelector(\'.ball3\')
    
    function animate(ball, distance, cb){
        setTimeout(function(){
            var marginLeft = parseInt(ball.style.marginLeft, 10)
            if(marginLeft === distance){
                cb && cb()
            }
            else {
                if(marginLeft < distance){
                    marginLeft++
                } else {
                    marginLeft--
                }
                ball.style.marginLeft = marginLeft + \'px\'
                animate(ball,distance,cb)
            }
        },13);
    }
    // animate(ball1, 100, function(){
    //     animate(ball2, 200, function() {
    //         animate(ball3, 300, function(){
    //             animate(ball3, 150, function(){
    //                 animate(ball2, 150, function(){
    //                     animate(ball1, 150, function(){

    //                     })
    //                 })
    //             })
    //         })
    //     })
    // })
    var Promise = window.Promise
    function promiseAnimate(ball, distance){
        return new Promise(function(resolve, reject){
            function _animate(){
                setTimeout(function(){
                    var marginLeft = parseInt(ball.style.marginLeft, 10)
                    if(marginLeft === distance){
                        resolve()
                    }
                    else {
                        if(marginLeft < distance){
                            marginLeft++
                        } else {
                            marginLeft--
                        }
                        ball.style.marginLeft = marginLeft + \'px\'
                        _animate()
                    }
                },13);
            }
            _animate()
        })

    }
    promiseAnimate(ball1, 100)
        .then(function() {
            return promiseAnimate(ball2,200)
        }).then(function(){
            return promiseAnimate(ball3,300)
        }).then(function(){
            return promiseAnimate(ball3,150)
        }).then(function(){
            return promiseAnimate(ball2,150)
        }).then(function(){
            return promiseAnimate(ball1,150)
        })
</script>
</html>

Promise就是对象,有三种状态: 未完成(pending), 已完成(fulfilled), 失败(rejected). 过程不可逆
Promise A与A+不同点
- A+规范通过术语thenable来区分promise对象
- A+定义onFulfilled/onRejected必须是作为函数来调用, 而且调用过程必须是异步的
- A+严格定义了then方法链式调用时onFulfilled/onRejected的调用顺序

使用promise改进之前的爬虫代码:

var http = require(\'http\')
var Promise = require(\'bluebird\')
var cheerio = require(\'cheerio\')        //npm install cheerio
var baseUrl = \'http://www.imooc.com/learn/\'
var url = \'http://www.imooc.com/learn/348\'
var videoIds = [728,637,197,348,259,75,134]

function filterChapters(html){
    var $ = cheerio.load(html)
    var chapters = $(\'.chapter\')
    var title = $(\'h2.l\').text()
    var number = $($(\'span.meta-value.js-learn-num\')).text()

    // courseData = {
    //     title: title,
    //     number: number,
    //     videos: [{
    //         chapterTitle: \'\',
    //         videos: [
    //             title: \'\',
    //             id: \'\'
    //         ]
    //     }]
    // }
    var courseData = {
        title: title,
        videos: [],
        number:number
    }
    chapters.each(function(item){
        var chapter = $(this)
        var chapterTitle = chapter.find(\'strong\').text().trim(\'\\n\').split(\'\\n\')[0]
        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().split(/\\s+/).slice(1,-2).join(\' \')
            var id = video.attr(\'href\').split(\'video/\')[1]
            chapterData.videos.push({
                title: videoTitle,
                id: id
            })

        })
        courseData.videos.push(chapterData)
    })
    return courseData
}

function printCourseInfo(coursesData){
    coursesData.forEach(function(courseData){
        // console.log(courseData.number + \' 人学过\' + courseData.title + \'\\n\')
        console.log(\'### \' + courseData.title + \'\\n\')
        courseData.videos.forEach(function(item){       
            console.log(item.chapterTitle);
            item.videos.forEach(function(video){
                console.log(\'   [\' + video.id + \']\' + video.title + \'\\n\')
            })
            
        })
    })
    // coursesData.forEach(function(item){
        
            
    // })
}
function getPageAsync(url){
    return new Promise(function(resolve,reject){
        console.log(\'正在爬取 \' + url)
        http.get(url, function(res) {
            var html = \'\'

            res.on(\'data\', function(data){
                html += data
            })

            res.on(\'end\', function(){
                resolve(html)
                // var courseData = filterChapters(html)
                // printCourseInfo(courseData)
            })
        }).on(\'error\', function(e){
            reject(e)
            console.log(\'获取课程数据错误\')
        })
    })

}

var fetchCourseArray = []

videoIds.forEach(function(id){
    fetchCourseArray.push(getPageAsync(baseUrl + id))
})

Promise
 .all(fetchCourseArray)
 .then(function(pages){
    var coursesData = []
    pages.forEach(function(html){
        var courses = filterChapters(html)
        coursesData.push(courses)
    })

    coursesData.sort(function(a,b){
        return a.number < b.number
    })
    printCourseInfo(coursesData)
 })

8. Buffer API

使用Buffer来读写图片的一个例子:

 1 var fs = require(\'fs\')
 2 
 3 fs.readFile(\'logo.png\', function(err, origin_buffer){
 4     console.log(Buffer.isBuffer(origin_buffer))
 5     fs.writeFile(\'logo_buffer.png\', origin_buffer, function(err){
 6         if(err) console.log(err)
 7     })
 8 
 9     // var base64Image = new Buffer(origin_buffer).toString(\'base64\')
10     var base64Image = origin_buffer.toString(\'base64\')
11 
12     console.log(base64Image)
13 
14     var decodedImage = new Buffer(base64Image, \'base64\')
15 
16     console.log(Buffer.compare(origin_buffer, decodedImage))
17 
18     fs.writeFile(\'logo_decodes.png\', decodedImage, function(err){
19         if(err) console.log(err)
20     })
21 })

9. Stream API

//拷贝文件
var fs = require(\'fs\')
var source = fs.readFileSync(\'../buffer/logo.png\')

fs.writeFileSync(\'stream_copy_logo.png\', source)

//拷贝图片
var fs = require(\'fs\')

var readStream = fs.createReadStream(\'stream_copy_logo.js\')
var n = 0

readStream
    .on(\'data\', function(chunk) {
        n++
        console.log(\'data emits\')
        console.log(Buffer.isBuffer(chunk))     //true  
        // console.log(chunk.toString(\'utf8\'))     //要读的文件的内容

        readStream.pause()
        console.log(\'data pause\')
        setTimeout(function(){
            console.log(\'data pause end\')
            readStream.resume()
        }, 3000)
    })
    .on(\'readable\', function(){
        console.log(\'data readable\')
    })
    .on(\'end\', function() {
        console.log(n)
        console.log(\'data ends\')
    })
    .on(\'close\', function() {
        console.log(\'data close\')
    })
    .on(\'error\', function(e){
        console.log(\'data read error\' + e)
    })

//拷贝视频
var fs = require(\'fs\')

var readStream = fs.createReadStream(\'1.mp4\')
var writeStream = fs.createWriteStream(\'1-stream.mp4\')

readStream.on(\'data\', function(chunk){
    //如果缓存区数据还在写, 那么暂停读数据
    if( writeStream.write(chunk) === false){
        console.log(\'still cached\')
        readStream.pause()
    }
})

readStream.on(\'end\', function(){
    writeStream.end()
})

writeStream.on(\'drain\', function() {
    console.log(\'data drains\')

    readStream.resume() 
})

10. 流与pipe

网络请求与pipe:

 1 var http = require(\'http\')
 2 var fs = require(\'fs\')
 3 var request = require(\'request\')
 4 
 5 http
 6     .createServer(function(req, res) {
 7         //=====================常规做法
 8         // fs.readFile(\'./buffer/logo.png\', function(err, data){
 9         //     if(err){
10         //         res.end(\'file not exist!\')
11         //     } else {
12         //         res.writeHeader(200, {\'Context-Type\' : \'text/html\'})
13         //         res.end(data)
14         //     }
15         // })
16 
17         //===============使用pipe方法读取本地图片
18         // fs.createReadStream(\'../buffer/logo.png\').pipe(res)
19 
20         //从网络上获取一张图片 在不保存的前提下再返回给浏览器
21         request(\'http://www.imooc.com/static/img/index/logo.png?t=1.1\').pipe(res)
22         //pipe会自动监听data和end事件. 可自动控制流量压力
23     })
24     .listen(8090)

使用pipe重构上面的copy视频的代码:

1 var fs = require(\'fs\')
2 fs.createReadStream(\'1.mp4\').pipe(fs.createWriteStream(\'1-pipe.mp4\'))

总结:

可读流是为了读取外部数据, 并把数据缓存到内部的buffer数组

可写流是为了消费数据, 从可读流里获取数据然后对得到的chunk数据库进行处理.

 1 var Readable = require(\'stream\').Readable
 2 var Writable = require(\'stream\').Writable
 3 
 4 var readStream = new Readable()
 5 var writeStream = new Writable()
 6 
 7 readStream.push(\'I \')
 8 readStream.push(\'Love \')
 9 readStream.push(\'Imooc\\n \')
10 readStream.push(null)
11 
12 writeStream._write = function(chunk, encode, cb) {
13     console.log(chunk.toString())
14     cb()
15 }
16 
17 readStream.pipe(writeStream)

一个自己定制的读写转换流的实现:

 1 var stream = require(\'stream\')
 2 var util = require(\'util\')
 3 
 4 function ReadStream(){
 5     stream.Readable.call(this)
 6 
 7 }
 8 
 9 util.inherits(ReadStream, stream.Readable)
10 
11 ReadStream.prototype._read = function(){
12     this.push(\'I \')
13     this.push(\'Love \')
14     this.push(\'Imooc\\n \')
15     this.push(null)
16 }
17 
18 function WriteStream(){
19     stream.Writable.call(this)
20     this._cached = new Buffer(\'\')
21 }
22 
23 util.inherits(WriteStream, stream.Writable)
24 
25 WriteStream.prototype._write = function(chunk, encode, cb){
26     console.log(chunk.toString())
27     cb()
28 }
29 
30 function TransformStream(){
31     stream.Transform.call(this)
32 }
33 
34 util.inherits(TransformStream, stream.Transform)
35 
36 TransformStream.prototype._transform = function(chunk, encode, cb){
37     this.push(chunk)
38     cb()
39 }
40 
41 TransformStream.prototype._flush = function(cb){
42     this.push(\'Oh Yeah!\')
43     cb()
44 }
45 
46 var rs = new ReadStream()
47 var ws = new WriteStream()
48 var ts = new TransformStream()
49 
50 rs.pipe(ts).pipe(ws)

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