Node learning

Global module

process.env environment variable

process.argv Command line variables
for example ：

// Command line input 
node index 11 22

//index.js
console.log(process.argv) //['.../node.exe'(node File directory ),'.../index'( Current file directory ),11,22]
console.log(parseInt(process.argv[2])+parseInt(process.argv[3])) //33

__dirname Current directory

System module

need require(), But you don't need to download it

path： Tools for handling file paths and directory paths

let path = require('path')

console.log(path.dirname('/node/a/b/1.jpg')) //  Directory path （/node/a/b/）
console.log(path.basename('/node/a/b/1.jpg')) //  file （1.jpg）
console.log(path.extname('/node/a/b/1.jpg')) //  File extension （.jpg）

Core applications ：

//index.js
let path = require('path')

console.log(path.resolve('/node/a/b','../../','c')) // node\c
console.log(path.resolve(__dirname,'index.js')) //  Get the absolute path to the file , Avoid making mistakes with relative paths 

fs： Used for reading and writing files

read ：

//a.txt
abc

//index.js
let fs = require('fs')

fs.readFile('a.txt',(err,data)=>{
    
	if(err){
    
		console.log(err)
	}else{
    
		console.log(data) //<Buffer 61 62 63>
		console.log(data.toString()) //abc
	}
})
// Synchronous writing 
let data2 = fs.readFireSync('a.txt')
console.log(data2)

Write ：

//index.js
let fs = require('fs')
// Overwrite 
fs.writeFile('b.txt',' a monthly salary 2000 element ',(err)=>{
    
	if(err){
    
		throw err
	}else{
    
		console.log(' Write successfully ') 
	}
})
// Additional writing 
fs.writeFile('b.txt',' a monthly salary 4000 element ',{
    flag:'a'},(err)=>{
    
	if(err){
    
		throw err
	}else{
    
		console.log(' Write successfully ') 
	}
})

// Synchronous writing 
fs.writeFileSync('b.txt',' a monthly salary 4000 element ')

Custom module

require

1. If there is a path, go to the path to find
2. If not, go node_modules Inside looking for
3. Finally, go to node In the installation directory of

exports： export
module： Batch

//mod.js
//exports.a = 'a'
//exports.b = 'b'
// The above export is equal to the following export 
module.exports = {
    
	a:'a',
	b:'b'
}

//index.js
const mod = require('./mod.js')
console.log(mod.a)//'a'
console.log(mod.b)//'b'

a key ：HTTP modular

//index.js
let http = require('http')
let fs = require('fs')

http.createServer((req,res)=>{
    
    console.log('req',req)
    fs.readFile(`./${
      req.url}`,(err,data)=>{
    
        if(err){
    
            res.writeHead(404)
            res.end('404 not found')
        }else{
    
            res.writeHead(200)
            res.end(data)
        }
    })
}).listen(8888)

GET request

//index.js
let http = require('http')
let url = require('url')

http.createServer((req,res)=>{
    
    console.log('req.url',req.url)
    //url.parse  The first parameter is the request path   The second parameter is whether to process query, If it is not processed, it is a spliced string 
    let {
    pathname,query} = url.parse(req.url,true)
    console.log(pathname,query)
}).listen(8888)

<!-- form.html -->
<form action="http://localhost:8888/login">
     user name ： <input type="text" name="username">
    <br>
     password ：<input type="password" name="password">
    <br>
    <input type="submit" value=" Submit ">
</form>

• url?user=xxx&pass=xxx
• <32K
• url modular
• url.parse(req.url,true)

POST request

//index.js
let http = require('http')
let querystring = require('querystring')

http.createServer((req, res) => {
    
    let result = []
    req.on('data', buffer => {
    
        result.push(buffer)
    })
    req.on('end', () => {
    
        let data = Buffer.concat(result).toString() // Because it is the receiving string , So you can directly tostring
        console.log(querystring.parse(data))
    })
    res.end('success')
}).listen(8888)

<!-- form.html -->
<form action="http://localhost:8888/login" method="POST">
     user name ： <input type="text" name="username">
    <br>
     password ：<input type="password" name="password">
    <br>
    <input type="submit" value=" Submit ">
</form>

• The data is usually placed in body In the body of the request , Big data , So it's received segment by segment
• < 2G
• querystring
• querystring.parse(data)

Comprehensive example

The directory structure is shown in the figure below ：

//index.js
let http = require('http')
let fs = require('fs')
let url = require('url')
let querystring = require('querystring')
const users = {
    
    'admin': '123456'
}

http.createServer((req, res) => {
    
    let path, postQuery, getQuery;
    if (req.method === 'GET') {
    
        let {
     pathname, query } = url.parse(req.url, true)
        path = pathname
        getQuery = query
        cb()
    } else if (req.method === 'POST') {
    
        path = req.url
        let result = []
        req.on('data', buffer => {
    
            result.push(buffer)
        })
        req.on('end', () => {
    
            postQuery = querystring.parse(Buffer.concat(result).toString())
            cb()
        })
    }

    function cb() {
    
        if (path === '/login') {
    
            res.writeHead(200, {
    
                'Content-Type': 'text/plain;charset=utf-8'
            })
            let {
     username, password } = getQuery

            if (!users[username]) {
    
                console.log(' The user doesn't exist ')
                res.end(JSON.stringify({
    
                    code: 401,
                    msg: ' The user doesn't exist '
                }))
            } else if (users[username] != password) {
    
                res.end(JSON.stringify({
    
                    code: 401,
                    msg: ' Incorrect password '
                }))
            } else {
    
                res.end(JSON.stringify({
    
                    code: 0,
                    msg: ' Login successful '
                }))
            }
        } else if (path === '/reg') {
    
            res.writeHead(200, {
    
                'Content-Type': 'text/plain;charset=utf-8'
            })
            let {
     username, password } = postQuery

            if (users[username]) {
    
                res.end(JSON.stringify({
    
                    code: 401,
                    msg: ' The user already exists '
                }))
            } else {
    
                users[username] = password
                res.end(JSON.stringify({
    
                    code: 0,
                    msg: ' Registered successfully '
                }))
            }
        } else {
    
            fs.readFile(`www${
      path}`, (err, data) => {
    
                if (err) {
    
                    res.writeHead(404)
                    res.end('404')
                } else {
    
                    res.end(data)
                }
            })
        }
    }
}).listen(8080)

<!-- login.html -->
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="jquery.min.js"></script>
</head>
<body>
         user name ： <input type="text" id="username">
        <br>
         password ：<input type="password" id="password">
        <br>
        <button id="login"> Submit </button>
        <br>
        <button id="reg"> register </button>

        <script > (function(){
       $('#login').click(function(){
       console.log('login click') $.ajax({
       url:'/login', method:'get', dataType:'json', data:{
       username:$('#username').val(), password:$('#password').val() }, success(res){
       if(res.code!==0){
       alert(res.msg) }else{
       alert(' Login successful ') location.href="index.html" } } }) }) $('#reg').click(function(){
       console.log('reg click') $.ajax({
       url:'/reg', dataType:'json', method:'post', data:{
       username:$('#username').val(), password:$('#password').val() }, success(res){
       if(res.code!==0){
       alert(res.msg) }else{
       alert(' Registered successfully ') } } }) }) })() </script>
</body>
</html>

summary

effect ：

1. Write webApi
2. Middle layer
3. Some of the front-end engineering （webpack、gulp）

thorough ：koa2/express、MongoDB/mysql etc.

Advanced

nodemon modular Hot update , use nodemon replace node Carry out orders , By increasing the nodemon.json Of watch Add listening files

DEBUG=*