一、Express中间件的概念与基本应用
const express = require('express')
// 加一个注释，用以说明，本项目代码可以任意定制更改
const app = express()
const PORT = process.env.PORT || 3000
// // 挂载路由
// app.use('/api', router)
// // 挂载统一处理服务端错误中间件
// app.use(errorHandler())
app.get('/', (req, res) => {
console.log(`${req.method}, ${req.url}, ${Date.now()}`);
res.send('/index')
})
app.get('/register', (req, res) => {
console.log(`${req.method}, ${req.url}, ${Date.now()}`);
res.send('/iregisterdex')
})
app.get('/login', (req, res) => {
console.log(`${req.method}, ${req.url}, ${Date.now()}`);
res.send('/login')
})
app.listen(PORT, () => {
console.log(`Server is running at http://localhost:${PORT}`)
})
封装个方法：
const express = require('express')
// 加一个注释，用以说明，本项目代码可以任意定制更改
const app = express()
const PORT = process.env.PORT || 3000
function logs(req) {
console.log(`${req.method}, ${req.url}, ${Date.now()}`);
console.log(`${req.method}, ${req.url}, ${Date.now()}`);
console.log(`${req.method}, ${req.url}, ${Date.now()}`);
}
app.get('/', (req, res) => {
logs(req)
res.send('/index')
})
app.get('/register', (req, res) => {
logs(req)
res.send('/iregisterdex')
})
app.get('/login', (req, res) => {
logs(req)
res.send('/login')
})
app.listen(PORT, () => {
console.log(`Server is running at http://localhost:${PORT}`)
})
发现也并不完美
写个中间件
const express = require('express')
// 加一个注释，用以说明，本项目代码可以任意定制更改
const app = express()
const PORT = process.env.PORT || 3000
app.use((req, res, next) => {
console.log(`${req.method}, ${req.url}, ${Date.now()}`);
next()
})
// // 挂载路由
// app.use('/api', router)
// // 挂载统一处理服务端错误中间件
// app.use(errorHandler())
// 中间件写在要使用的逻辑前面
app.get('/', (req, res) => {
res.send('/index')
})
app.get('/register', (req, res) => {
res.send('/register')
})
app.get('/login', (req, res) => {
res.send('/login')
})
app.listen(PORT, () => {
console.log(`Server is running at http://localhost:${PORT}`)
})
二、不同中间件类别的使用方式
中间件分类：
- 应用程序级别中间件
- 路由级别中间件
- 错误处理中间件
- 内置中间件
- 第三方中间件
1、应用程序级别中间件
const express = require('express')
const app = express()
const PORT = process.env.PORT || 3000
// 以下3个都是应用程序级别中间件
app.use((req, res, next) => {
console.log(`${req.method}, ${req.url}, ${Date.now()}`);
next()
})
app.get('/', (req, res) => {
res.send('/index')
})
app.get('/user', (req, res, next) => {
console.log(req.method)
next()
}, function (req, res, next){
console.log('666')
next()
res.send('/user')
})
app.listen(PORT, () => {
console.log(`Server is running at http://localhost:${PORT}`)
})
2、路由级别中间件
router/index.js
const express = require('express')
const router = express.Router()
router.get('/', (req, res) => {
console.log(req.methods)
res.send('/index')
})
router.get('/user', (req, res) => {
console.log(req.methods)
res.send('/user')
})
module.exports = router
app.js
const express = require('express')
const app = express()
const router = require('./router/index')
const routerVideo = require('./router/video')
const PORT = process.env.PORT || 3000
// 挂载路由
// app.use(router)
app.use('/api', router) // 添加前缀
// app.use('/video', routerVideo) // 添加前缀
app.listen(PORT, () => {
console.log(`Server is running at http://localhost:${PORT}`)
})
3、错误处理中间件
// 错误处理中间件
app.use((err, req, res, next) => {
console.log(err)
res.status(500).send('service Error')
})
4、 内置中间件
// app.use(express.urlencoded())
app.use(express.json())