node.js Foundation

events 事件有两种：

System Events  C++ Core libuv

Custom Events  JavaScript Core Event Emitter

一.The node event emitter

1.创建 Emitter module

新建 emitte.js文件

代码如下

function Emitter(){
this.events = {};
}
// 为事件注册监听器
Emitter.prototype.on = function(type,listener) {
this.events[type] = this.events[type]||[];
this.events[type].push(listener);
};

//发射，something happend, listener responed
Emitter.prototype.emit = function(type){
if (this.events[type]){
this.events[type].forEach(function(listener){
			listener();
})
}
}

module.exports = Emitter;

2.引入emitter 模块

创建app.js 文件

代码如下

 
 var Emitter = require('./emitter');
 
 var emtr = new Emitter();
 
 emtr.on('greet',function(){
	 console.log('Somewhere,some said hello.');
 }); //注册事件以及监听器

emtr.on('greet',function(){
	console.log('A greet occured!');
})

emtr.emit('greet');

二.node.js中的events模块

使用nodejs 中的emit

将上述app.js 改为

 
 var Emitter = require('events');
 
 var emtr = new Emitter();
 
 emtr.on('greet',function(){
	 console.log('Somewhere,some said hello.');
 }); //注册事件以及监听器

emtr.on('greet',function(){
	console.log('A greet occured!');
})

emtr.emit('greet');

但是以上使用string 注册事件的方式容易出错

新建config.js文件

代码如下：

module.exports = {
	events :{
		GREET:'greet',
		FILESAVED:'filesaved'
}
}

现在修改app.js文件如下：

 
 var Emitter = require('events');
 var eventConfig = require('./config')
 
 var emtr = new Emitter();
 
 emtr.on(eventConfig.greet,function(){
	 console.log('Somewhere,some said hello.');
 }); //注册事件以及监听器

emtr.on(eventConfig.greet,function(){
	console.log('A greet occured!');
})

emtr.emit(eventConfig.greet);

这样有利于代码的维护升级

三. Object.create prototypes

使用Object.create 生成object 的原型

创建 app.js ,代码如下：

var person = {
	firstname: '',
	secondname:'',
	greet: function(){
return this.firstname+' '+this.lastname;
}
}

var john = Object.create(person);

john.firstname = 'John'
john.lastname = 'Doe';

var jane = Object.create(person);

jane.firstname = 'Jane';
jane.lastname = 'Doe';

console.log(john.greet());
console.log(jane.greet());

四.Inheriting from event emitter

创建 app.js,使用util模块中的 inherits 来继承原型

代码如下

var EventEmitter = require('events');
var util  = require('util');

function Greeter(){
this.greeting  = 'Hello world!';
}

util.inherits(Greeter,EventEmitter);

Greeter.prototype.greet = function(data){
	console.log('Hello,this is '+data);
this.emit('greet',data);
}

var greeter = new Greeter();
greeter.on('greet',function(data){
	console.log('Hello ,this is an events : '+data);
});

greeter.greet('Tony');

五.ECMAScript 6

literal strings

var name = 'Nike';

var greet = `Hello ${name}`;

console.log(greet);

call and apply

用于改变调用者 this

var obj = {
	name:'John Doe',
	greet: function(){
		console.log(this.name);
}
}

obj.greet.call({name : 'Jane Doe'});
obj.greet.apply({name: 'Jane Doe'});

 
var util = require('util');

function Person(){
this.firstname = 'John';
this.lastname = 'Doe';
}

Person.prototype.greet = function (){
	console.log('Hello '+this.firstname + ' '+ this.lastname);
}

function Policeman(){
Person.call(this);//very important 
this.badgenumber = '1234';
}
util.inherits(Policeman,Person);

var pol=  new Policeman();
pol.greet();

Javascript 同步的

Nodejs 异步的

Event Driven No-Blocking I?O in V* javascript

no-blocking : do other things without stopping your programing from running

Buffer

the relationship between buffer and stream

缓冲区 Buffer的使用：

var buf  = new Buffer('Hello','utf8');
console.log(buf);
console.log(buf.toString());
console.log(buf.toJSON());
console.log(buf[2]);
buf.write('wo');
console.log(buf.toString()); //wollo, 会覆盖缓冲区

Files and fs

ERROR_FIRST CALLBACK:

callbacks takes an error object as the first parameters;

CHUNK:

A piece of data sent through  a stream

Data is split in 'chunks'  and streamed

var fs = require('fs');
var greet = fs.readFileSync(__dirname+'/greet.txt','utf8');

console.log(greet);

var greet2 = fs.readFile(__dirname+'/greet.txt',function(err,data){
	console.log(data.toString());
});
console.log('Done');

things about createWriteStream createReadStream

var fs = require('fs');
var readable = fs.createReadStream(__dirname+'/greet.txt',{encoding: 'utf8',highWaterMark: 16*1024});
var writable = fs.createWriteStream(__dirname + '/greatcopy.txt');
readable.on('data',function(chunk){
	console.log(chunk.length);
	writable.write(chunk);
});

pipe

var fs = require('fs');
var zlib = require('zlib');
var readable = fs.createReadStream(__dirname+'/greet.txt' );

var writable = fs.createWriteStream(__dirname + '/greatcopy.txt');
 
 var compressed = fs.createWriteStream(__dirname + '/great.txt.gz');
 var gzip = zlib.createGzip();
 
 readable.pipe(writable);
 
 readable.pipe(gzip).pipe(compressed);

HTTP_PARSER

var  http = require('http');

http.createServer(function(req,res){

	res.writeHead(200,{'Content-Type':'text/plain'})
	res.end('Hello world\n');

}).listen(1337,'127.0.0.1');

引入html 文件

var  http = require('http');
var fs = require('fs');
http.createServer(function(req,res){

	res.writeHead(200,{'Content-Type':'text/html'});
var html = fs.readFileSync(__dirname+'/index.html');
	res.end(html);

}).listen(1337,'127.0.0.1');

var  http = require('http');
var  fs = require('fs');
http.createServer(function(req,res){

	res.writeHead(200,{'Content-Type':'text/html'});
var html = fs.createReadStream(__dirname+'/index.html').pipe(res) 

}).listen(1337,'127.0.0.1');

OutPut  JSON

JSON.stringify(obj)

var  http = require('http');
var  fs = require('fs');
http.createServer(function(req,res){

	res.writeHead(200,{'Content-Type':'application/json'});
var obj = {
		firstname:'John',
		lastname:'Doe'
};

	res.end(JSON.stringify(obj));

}).listen(1337,'127.0.0.1');

Routing:

mapping  http requests to  contents

var  http = require('http');
var  fs = require('fs');
http.createServer(function(req,res){

if(req.url === '/'){
	fs.createReadStream(__dirname+'/index.html').pipe(res);
}
if(res.url === '/api'){
	res.writeHead(200,{'Content-Type':'application/json'});
var obj = {
		firstname:'John',
		lastname:'Doe'
};
	res.end(JSON.stringify(obj));
 }
 
 res.writeHead(404);
 res.end();

}).listen(1337,'127.0.0.1');

使用 npm

进入文件夹

npm init ;

npm install moment

发布文件后，删除node_modules后，

使用npm install

--save 添加到package.json 文件中

npm install jasmine-node --save-dev  开发依赖模块

npm install -g nodemon   全局安装

npm update ,更新所有的dependencies

使用别人的代码

var express = require('express');

var app = express();

var port = process.env.PORT || 3000;
app.use('/assets',express.static(__dirname+'/public'));
app.use('/',function(req,res,next){
	console.log('Request Url: ' + req.url);
	next();
})
app.get('/',function(req,res){
	res.send('<html><head><link href = assets/style.css type =text/css rel = stylesheet /></head><body><h1>Hello world</h1></body></html>');
});

app.get('/person/:id',function(req,res){
	res.send('<html><body><h1> Person: '+req.params.id+'</h1></body></html>');
})
app.get('/api',function(req,res){
	res.send('<html><body><h1>Hello world</h1></body></html>')
})

app.listen(port);

var express = require('express');

var app = express();

var port = process.env.PORT || 3000;
app.use('/assets',express.static(__dirname+'/public'));

app.set('view engine','ejs')

app.use('/',function(req,res,next){
	console.log('Request Url: ' + req.url);
	next();
})

app.get('/person/:id',function(req,res){
	res.render('person',{ID: req.params.id,QStr: req.query.qstr});
})

app.listen(port);

person.ejs:

<html>
<head>
<link href ='assets/styl.css' type = "text/css" ref= "stylesheeet" />
</head>
<body>
 <h1>Peson: <%=ID %> </h1>
 <h2>Query String Value: <%= QStr %> </h2>
</body>
</html>

npm install body-parser

var express = require('express');
var bodyParser = require('body-parser');
var app = express();

var urlencodedParser = bodyParser.urlencoded({extended: false});
var jsonParser = bodyParser.json();
var port = process.env.PORT || 3000;
app.use('/assets',express.static(__dirname+'/public'));
app.set('view engine','ejs')

app.get('/',function(req,res){
	res.render('index'); 
})

app.get('/person/:id',function(req,res){
	res.render('person',{ID: req.params.id,QStr: req.query.qstr});
})

app.post('/person',urlencodedParser,function(req,res){
	 res.send('Thank You!');
	 console.log(req.body.firstname);
	 console.log(req.body.lastname);
})

app.post('/personjson',jsonParser,function(req,res){
	res.send('Thank you jsonParser');
	 console.log(req.body.firstname);
	 console.log(req.body.lastname);
})

app.listen(port);

index.ejs

<html>
<head>
<link href ='/assets/styl.css' type = "text/css" ref= "stylesheeet" />
    <script src = "http://ajax.aspnetcdn.com/ajax/jQuery/jquery-2.1.4.min.js"></script>
</head>
<body>
<h1>Hello World!</h1>
<form method ='POST' action="/person"> 
 	First name: <input type ="text" id ="firstname" name ="firstname"/><br>
Last  name: <input type ="text" id= "lastname" name= "lastname"/><br>
<input type ="submit" value ="submit"/>
 </form>
 <script>
	 $.ajax({
	 	 type: "POST",
		 url: "/personjson",
		 data: JSON.stringify({firstname: "John",lastname:"Doe"}),
		 dataType: 'json',
		 contentType: 'application/json'
 })
 </script>
</body>
</html>

mongoose

来自为知笔记(Wiz)