Detailed explanation of express framework

Express

Use express You can quickly create web Web server or API Interface server

1. establish express Of web The server

//  Import express
const express = require("express")
//  establish web The server 
const app = express()
//  start-up web The server 
app.listen(8088,()=>{
	console.log('http://127.0.0.1:8088');
})

2. monitor get/post request

//  monitor GET Request and return the response content , The first parameter is the requested url
app.get('/get',(req,res)=>{
	//req.query Get request is the parameter sent 
	console.log(req.query)//http://127.0.0.1:8088/get?name=zs&age=18
	//{ name: 'zs', age: '18' }
	//  call express Provided res.send() Method , Set the returned JSON object 
	res.send({name:"zs",age:20,gender:" male "})
 })
 
//  monitor POST Request and return the response content , The first parameter is the requested url
app.post('/post',(req,res)=>{
	//  call express Provided res.send() Method , Set the returned JSON object 
	res.send({name:"zs",age:20,gender:" male "})
})

 towards http://127.0.0.1:8088/post The return value of the send request is 
{   "name": "zs",
    "age": 20,
    "gender": " male "}

3. To obtain parameters

// Static parameters 
app.get('/get',(req,res)=>{
	//req.query Get request is the parameter sent 
	//http://127.0.0.1:8088/get?name=zs&age=18
	res.send(req.query)
	//{ name: 'zs', age: '18' }
 })

// Dynamic parameters 
app.get('/getId/:id',(req,res)=>{
	//req.query Get request is the parameter sent 
	//http://127.0.0.1:8088/getId/12
	res.send(req.params)
 })
 // return 
 {
    "id": "12"
}
// Multiple dynamic parameters 
app.get('/getId/:id/:name',(req,res)=>{
	//req.query Get request is the parameter sent 
	//http://127.0.0.1:8088/getId/12/zs
	res.send(req.params)
 })
 // return 
 {
    "id": "12"
    "name":"zs"
}

4. middleware

//app.use() The function is to register the global middleware ,app.use('path',function()) The first parameter is the path. If it is / Omission 

express There are three kinds of middleware 
1. Built in middleware  static
2. Custom middleware 
3. Third-party middleware  (body-parser) ( Interceptor )

app.use(express.static('public'))
app.use(express.static('dome'))
// You can directly access 
http://127.0.0.1:8088/index.html
http://127.0.0.1:8088/index.css
http://127.0.0.1:8088/index.js

// Will prioritize public In the document index file , If you can't find it, find dome Medium index file 

app.use('/public',express.static('public'))
// To access http://127.0.0.1:8088/public/index.html

// Customize the middleware with global effect   Multiple middleware can be defined , The middleware will be called in sequence 
app.use(function (req, res, next) {/* Indicates that it matches any route */
    console.log(new Date())
    next()/* Indicates that the middleware will continue to execute after the matching is completed .*/
})
// Local middleware 
let func = function (req, res, next) {/* Indicates that it matches any route */
    console.log(new Date())
    next()/* Indicates that the middleware will continue to execute after the matching is completed .*/
}
// Multiple local middleware can be defined 
app.get('/',func1,func2,(req,res)=>{
	res.send('get router by :/')
})

// Use middleware to process request data 
app.use(express.json())
app.use(express.urlencoded({extended:false})

// Use third-party middleware  (body-parser) ( Interceptor )
1. npm install body-parser
// To middleware 
const parser = require("body-parser")
// Register middleware 
app.use(parser.urlencoded({extended:false})

//nodejs built-in querystring The module processes the query string and converts the query string into object format 
const qs = require("querystring")
console.log(qs.parse(str))

5. nodemon

 It can start the modified project less frequently ,nodemon It will automatically restart the project to facilitate development and testing 
npm install -g nodemon

 Use nodemon app.js To run the project , no need node app.js

6. route

1.  Mount in the original way 
const express = require("express")

const app = express();

//  Mount route 
app.get('/',(req,res)=>{
	res.send('get router by :/')
})

app.post('/',(req,res)=>{
	res.send('post router by :/')
})

app.listen(8088,()=>{
	console.log("http://127.0.0.1:8088");
})

2. Use express route 
// stay router.js Create a routing object in 
const express = require("express")
const router = express.Router();

//  Mount specific routes 
router.get('/user/list',(rep,res)=>{
	res.send("GER user list")
})

router.post("/user/add",(req,res)=>{
	res.send("POST user add")
})

//  Export routing objects out 
module.exports = router

// stay index.js Reference route in 
const express = require("express")
const app = express()
//  Import routing module 
const router = require("./router")
//  Register routing module 
app.use(router)

app.listen(8088,()=>{
	console.log("http://127.0.0.1:8088");
})

//app.use('/api',router)// Add a uniform prefix to the route http://127.0.0.1:8088/api/user/add

7. To write get/post Interface

const express = require("express");

const app = express()

const router = express.Router()
app.use(express.urlencoded({extended:false}))
router.get('/get',(req,res)=>{
	//  Request data sent by the client 
	const query = req.query;

	res.send({
		status:0,//0 It means success ,1 It means failure 
		msg:"GET The request is successful ",// Description of the State 
		data:query// Data that needs to be responded to the client 
	})
})

router.post('/post',(req,res)=>{
	//  Request data sent by the client 
	const body = req.body;
	//  Configure the middle price of parsing form data 
	res.send({
		status:0,//0 It means success ,1 It means failure 
		msg:"POST The request is successful ",// Description of the State 
		data:body// Data that needs to be responded to the client 
	})
})
app.use(router);
app.listen(8088,()=>{
	console.log("get request ");
})

8.cors Cross domain solution

const express = require("express");
const cors = require("cors")
const app = express()
// Use third-party middleware to solve cross domain 
app.use(cors())

// Customize cors Set up cross domain requests 
var cors = function(req,res,next()){
  res.header('Access-Control-Allow-Origin', 'http://localhost:8088');// Request address 
  res.header('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE');// Request mode 
  res.header('Access-Control-Allow-Headers', 'Content-Type');// Request header 
  next()
  }
app.use(cors)