express入门学习

Posted 2020-09-18 aGod

一、安装express

cnpm || npm  install express --save ;

1. Hello  World

var express = require(‘express‘);

var app = express();

app.get(‘/‘,function(req,res){
    res.send(‘hello world‘);
});

var server = app.listen(‘3000‘,function(){
    var host = server.address().address;
    var port = server.address().port;

    console.log(‘server start localhost‘,host,port);
})

2.express路由

var express = require(‘express‘);

var app = express();

//http://localhost:3000/
app.get(‘/‘,function(req,res){
    res.send(‘hello world‘);
});
//http://localhost:3000/user.html
app.get(‘/user.html‘,function(req,res){
    res.sendFile(__dirname + ‘/‘ + ‘user.html‘);
});
//http://localhost:3000/index.html
app.get(‘/index.html‘,function(req,res){
    res.sendFile(__dirname + ‘/‘ + ‘index.html‘)
});
/*
 *其实每个路由对于着每个方法，把 req() => 请求的api 看懂
 * 
 * 把 res(); => 的api  看会。就知道怎么和服务端交换啦。
 * 
 * 当客户端发送AJAX请求的时候，其实就是方法的每个方法。
 * 
 */

var server = app.listen(‘3000‘,function(){
    var host = server.address().address;
    var port = server.address().port;

    console.log(‘server start localhost‘,host,port);
})

3.静态资源 app.user(express.statice(‘public‘));

var express = require(‘express‘);

var app = express();

//设置静态资源的位置

app.use(express.static(‘public‘));

//http://localhost:3000/img/1.jpg

//public/img/1.jpg
var server = app.listen(‘3000‘,function(){
    var host = server.address().address;
    var port = server.address().port;

    console.log(‘server start localhost‘,host,port);
})

二、express的中间件

1.应用级中间件

var express = require(‘express‘);

var app = express();

// 没有挂载路径的中间件，应用的每个请求都会执行该中间件
app.use(function(req,res,next){

    console.log(‘应用级中间件‘);
    console.log(‘time‘ + Date.now());
    next();
})

app.get(‘/‘,function(req,res){
    res.send(‘我是 根路径‘)
});

// 挂载至 /user/:id 的中间件，任何指向 /user/:id 的请求都会执行它
app.get(‘/user/:id‘,function(req,res,next){
    console.log(‘我是 user路由上面的子中间件‘);

    next();
});
app.get(‘/user/:id‘,function(req,res){
    var id = req.params.id;

    res.send(id);
});

app.get(‘/method/:id‘,function(req,res,next){
    console.log(‘methos路径的参数‘,req.params);

    next();
},function(req,res,next){
    console.log(‘methods路径的第二个参数‘,req.method)
    next();
})

app.get(‘/method/:id‘,function(req,res){
    var path = req.route;

    res.send(path);
});
var server = app.listen(‘3000‘,function(){
    var host = server.address().address;
    var port = server.address().port;
    console.log(‘server start localhost‘,host,port);
})

2.路由级中间件 express.Router();

var express = require(‘express‘);
var router = express.Router();
var app = express();

router.use(function(req,res,next){
    console.log(req.path);
    next()
});

router.get(‘/user/:id‘,function(req,res,next){
    console.log(req.originalUrl);
    next();
})

router.get(‘/user/:id‘,function(req,res){
    res.send(req.params);
})
app.use(‘/‘,router)
var server = app.listen(‘8080‘,function(){
    console.log(‘start‘)
});

3.错误级中间件

var express = require(‘express‘);
var app = express();

app.use(function(error,req,res,next){
    res.status(‘500‘).send(‘something error‘);
})

var server = app.listen(‘3000‘,function(){
    console.log(‘server start‘);
})

4.静态资源中间件 express.static();

三、模板引擎

1.安装jade模板引擎,cnpm || npm install jade --save

var express = require(‘express‘);
var app = express();

app.set(‘views‘,‘./views‘);
app.set(‘view engine‘,‘jade‘);

app.get(‘/‘,function(req,res){
    res.render(‘index‘,{title:‘jade‘,message:‘模板引擎‘})
});

var server = app.listen(‘3000‘,function(req,res){
    console.log(‘server start‘);
})

2.view 下面的index.jade

html
  head
    title!= title
  body
    h1!= message