07. Express routing

1、 What is routing

【 explain 】： Broadly speaking , Routing is a mapping relationship .

【 Explanation of life cases 】：

2、Express The routing

【 explain 】： Routing refers to the mapping between client requests and server processing functions .

【 Grammar format 】：

app.METHOD(PATH ,HANDLER)

【 Case study 】：

const express = require('express')
const app = express()
//  Mount route 
app.get('/', (req, res) => {
    
    res.send('hello world！！')
})

app.post('/', (req, res) => {
    
    res.send('Post Request')
})

app.listen(80, () => {
    
    console.log('express running at http://127.0.0.1');
})

3、 Route matching process

【 explain 】： Every time a request arrives at the server , A match that needs to be routed first , Only after the match is successful , Will call the corresponding processing function .

【 The illustration 】：

【 matters needing attention 】：

• Match in defined order
• The type of request and the type of request URL Simultaneous matching , Will call the corresponding processing function

4、 Use of routes

1、 Basic use

【 explain 】： stay Express The easiest way to use routing in , Is to mount the route to app On

【 Code example 】：

const express = require('express')

const app = express()

//  Mount route 
app.get('/', (req, res) => {
    
    res.send('hello world！！')
})

app.post('/', (req, res) => {
    
    res.send('Post Request')
})

app.listen(80, () => {
    
    console.log('express running at http://127.0.0.1');
})

2、 Modular routing

【 Creating steps 】：

• Create the corresponding route js file
• call express.Router() Function to create a routing object
• Mount the specific route to the routing object
• Use moudle.exports Share routes outward
• Use app.use() Function register route

【 Code case 】：

• route user.js file

//1、 Import express
const express = require('express')
//2、 Create routing objects 
const router = express.Router()
//3、 Define specific routes 
router.get('/user', (req,res)=>{
    
	res.send('Get User List！！！')
})

router.post('/User/add', (req,res)=>{
    
	res.send('Add new user!!!')
})
//4、 Export route 
module.exports=router

• Register and use routing

const userRouter = require('./user.js')
// Use app.use() Register routing module 
app.use(userRouter)

3、 Add prefix to the routing module

【 demonstration 】：

const userRouter = require('./user.js')
// Use app.use() Register routing module 
app.use('/api', userRouter)