Express route

What is routing

Broadly speaking , Routing is a mapping relationship .

Real life routing ：

ad locum , Routing is the mapping relationship between keys and services

stay Express The middle path refers to the mapping relationship between the client's request and the server's processing function .
Express The routing in is divided into 3 Part of it is made up of , Namely Type of request 、 Requested URL Address 、 Processing function , The format is as follows ：

Routing matching process

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 .

In the match , Will match in the order of routing , If the request type and the requested URL At the same time, the match is successful , be Express Will send this request , Forward to the corresponding function Function to process .

Considerations for route matching ：

• Match in defined order
• The type of request and the type of request URL At the same time, the match is successful , Will call the corresponding processing function

Simplest route use

stay Express The easiest way to use routing in , Is to mount the route to app On , The sample code is as follows ：

const express = require('express')
// establish Web The server , Name it app
const app = express()

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

// start-up Web The server 
app.listen(80, () => {
    
  console.log('http://127.0.0.1')
})

Modular routing

In order to facilitate the modular management of routing ,Express It is not recommended to mount the route directly to app On , Instead, it's recommended to pull the route out into a separate module . The steps to extract a route into a separate module are as follows ：
① Create the routing module corresponding to .js file
② call express.Router() Function to create a routing object
③ Mount the specific route to the routing object
④ Use module.exports Share routing objects out
⑤ Use app.use() Function registration routing module

for example ：

Create routing module ：

//  This is the routing module 
// 1.  Import  express
const express = require('express')
// 2.  Create routing objects 
const router = express.Router()

// 3.  Mount specific routing 
router.get('/user/list', (req, res) => {
    
  res.send('Get user list.')
})
router.post('/user/add', (req, res) => {
    
  res.send('Add new user.')
})

// 4.  Export routing objects out 
module.exports = router

Register routing module ：

const express = require('express')
const app = express()

// 1.  Import routing module 
const router = require('./03.router')
// 2.  Register routing module 
app.use(router)

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

Be careful ： app.use() Function function , Is to register the global middleware

Prefix routing module

Similar to when hosting static resources , Uniformly mount access prefixes for static resources , The way the routing module adds a prefix is also very simple ：