express组件学习

一、express

可以做：web application、api...

特性：

适合写简单的路由系统
集成很多模板引擎
中间件系统

二、请求与响应

var express = require('express');

var app = express();

//据说第二个参数是一个中间件方法
app.get('/', function(req, res) {
    //学会查api来学习更多知识，学会学习官方api文档
    var resObj = req.method;
    //send可以发送字符串、json（包含自动stringify）对象和数组
    res.send(resObj);
})

app.listen(3000);
console.log('listening to port 3000');

三、路由参数

server.js

var express = require('express');

var app = express();

app.get('/profile/:id/user/:name', function(req, res) {
    console.dir(req.params);
    res.send('you requested to a profile page with the name of ' + req.params.name);
})

app.listen(3000);
console.log('listening to port 3000');

terminal

chrome

四、查询字符串

server.js

app.get('/', function(req, res) {
    console.dir(req.query);
    res.send('home page:' + req.query.find);
})

terminal

chrome

五、post请求和postman工具

同时处理x-www-form和json

var express = require('express');
var bodyparser = require('body-parser');

var app = express();

//create application/json parser
var jsonParser = bodyparser.json();

//create application/x-www-form-urlencoded parser
var urlencodedParser = bodyparser.urlencoded({ extended: false})

app.post('/', urlencodedParser,function (req, res) {
    console.dir(req.body);
    res.send(req.body.name);
})

app.post('/upload', jsonParser, function (req, res) {
    console.dir(req.body);
    res.send(req.body.name);
})

参考链接：github/express/body-parser

六、上传文件

form.html

<body>
    <form action="/upload" method="post" enctype="multipart/form-data">
        <h2>单图上传</h2>
        <input type="file" name="logo">
        <input type="submit" value="submit">
    </form>
</body>

server.js

var express = require('express');
var bodyparser = require('body-parser');
var fs = require('fs');
var multer = require('multer');
var upload = multer({ dest: 'uploads/'});
var app = express();

//create application/json parser
var jsonParser = bodyparser.json();

//create application/x-www-form-urlencoded parser
var urlencodedParser = bodyparser.urlencoded({ extended: false})

app.get('/', function(req, res) {
    console.dir(req.query);
    res.send('home page:' + req.query.find);
})

app.get('/form', function(req, res) {
    var form = fs.readFileSync('./form.html', { encoding: 'utf8'});
    res.send(form);
})

app.post('/', urlencodedParser,function (req, res) {
    console.dir(req.body);
    res.send(req.body.name);
})

app.post('/upload', upload.single('logo'),function (req, res) {
    res.send({'ret_code': 0});
})

app.listen(3000);
console.log('listening to port 3000');

结构变化

参考链接：github/express/multer

tips:

app.get('/form', function(req, res) {
    var form = fs.readFileSync('./form.html', { encoding: 'utf8'});
    res.send(form);
})

等价于

app.get('/form', function(req, res) {
    res.sendFile(__dirname + '/form.html');
})

七、模板引擎

引入

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

使用

server.js

app.get('/form/:name', function(req, res) {
    var person = req.params.name;
    res.render('form', { person: person});
    res.sendFile(__dirname + '/form.html');
})

form.ejs

<h1><%= person %></h1>

遍历数组

<ul>
    <%= data.hobbie.forEach(function(item){ %>
        <li>
            <%= item %>
        </li>
    <%= }) %>
</ul>

公用模板

使用

<%- include('partials/header.ejs') -%>

about.ejs

<body>
    <%- include('partials/header.ejs') -%>
</body>

渲染

app.get('/about', function(req, res) {
    var data = {age: 29, job: 'programmer', hobbie: ['eating', 'fighting', 'fishing']};
    res.render('about', { data: data});
})

参考链接：ejs.co、pug

八、中间件

解释：请求与响应之间的处理过程是中间件发挥作用的地方。

好处：共用模块、全局性的操作

类型：

应用级中间件
路由级中间件
错误层次中间件
内置中间件
第三方中间件

执行顺序

app.use(function(req, res, next){
    console.log('1');
    next();
    console.log('3');
})

app.use(function(req, res, next){
    console.log('2');
})

路由中间件

server.js

var indexRouter = require('./routes/index.js');
var userRouter = require('./routes/user.js');

app.use('/', indexRouter);
app.use('/users', userRouter);

./route/index.js

var express = require('express');

var router = express.Router();

router.get('/', function(req, res, next) {
    res.send('root');
})

module.exports = router;

./route/user.js

var express = require('express');

var router = express.Router();

router.get('/', function(req, res, next) {
    res.send('user');
})

module.exports = router;

体会：用中间件写路由的好处

参考链接：express/using-middleware