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Learning notes of nodejs

2020-11-09 10:50:25 My sister is talking nonsense

Two 、node An introduction to the

node It's a run js Environment . Browsers also run js Environment .

The difference between the two is :

  • The browser will have window and document Call to . however node No,
  • node There are many modules of api, For example, file system access
  • node You can switch the running environment ( Switch versions ?)
  • node no need bable transformation
  • node It uses commonJS, To use require

2-2 nodejs And js The difference between

nodejs = nodejsapi + ecmascript
Handle http, Processing documents, etc .

2-3 commonjs

module.export()
require

2-4,5 debuger And inspect agreement

--inspect==9229

chrome://inspect/#devices

Four 、 Develop the interface of blog project

4-1 http summary

from url The process to the browser ?

First dns analysis , After parsing, send the request , adopt http The establishment of the agreement tcp link , And then transfer the file .
The browser takes the data and builds dom Trees , establish css Trees . Merge into render Trees , Then render , Inject js.

DNS analysis , establish TCP Connect , send out http request
server Received http request , Process and return .
The client receives the returned data , Processing data ,( Such as rendering the page , perform js)

image.png
Remote address Namely dns Result of query

4-4 Handle http A comprehensive example of a request

const http = require("http");
const port = 3000

const server = http.createServer((req, res) => {
    res.setHeader("Content-Type", "application/json")
    const url = req.url
    const method = req.method
    res.end(`${url}${method}`);
})

server.listen(port, () => {
    console.log(` The server is running at  http://localhost:${port}/`)
})
console.log("ok")

4-5 Build development environment

  • Use nodemon Detect file changes , Automatic restart node.
  • corss-env Set the environment variable

npm i nodemon cross-env --save-dev

  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "dev": "cross-env NODE_ENV=dev nodemon  ./bin/www.js"
  },

4-6 Initialize route

image.png

hostname:nodejs.cn
pathname:/api/blog/list
query:?name=zhangsan&keyword=123

const method = res.method  // post get
const url  = res.url // url
const path = res.url.split("?")[0] // 

4-7 Develop routing

establish SuccessModelErrorModel .

class BaseModel {
    constructor(data, message) {
        if (typeof data === "string") {
            this.message = data;
            message = null;
            data = null
        }
        if (data) {
            this.data = data;
        }
        if (message) {
            this.message = message;
        }
    }
}

class SuccessModel extends BaseModel {
    constructor(data, message) {
        super(data, message);
        this.error = 0
    }
}

class ErrorModel extends BaseModel {
    constructor(data, message) {
        super(data, message);
        this.error = -1
    }
}

module.exports = {
    SuccessModel,
    ErrorModel
}

4-8 Develop routing ( Blog details routing )

const fs = require('fs');
const path = require('path');
function getFileContent(fileName) {
    const fullFileName = path.resolve(__dirname, 'file', fileName)
    const promise = new Promise((resolve, reject) => {
        fs.readFile(fullFileName, (err, data) => {
            if (err) {
                reject(err);
            }
            resolve(JSON.parse(data));
        })
    })
    return promise;
}
getFileContent('a.json').then(aDate => {
    console.log(aDate);
    return getFileContent(aDate.next);
}).then((bData) => {
    console.log(bData);
    return getFileContent(bData.next);
}).then((cData) => {
    console.log(cData);
});

4-9 Develop routing ( Handle POSTData)

//  Used for processing post data
const getPostData = (req) => {
    const promise = new Promise(() => {
        if (req.method !== 'POST') {
            resolve({})
            return
        }
        if (req.headers['content-type'] !== "application/json") {
            resolve({})
            return
        }
    })
    //  Listening to stream data 
    let postData = ''
    res.on('data', chunk => {
        postData += chunk.toString()
    })
    res.on('end', () => {
        if (!postData) {
            resolve({})
            return
        }
        resolve(
            JSON.parse(postData)
        )
    })
    return promise
}

Update and delete data, etc ....

5 database

MySql

use myblog;
--  Look up the table 
-- show tables;
-- insert into blogs(title,content,createtime,author)values(" Ms. Hu 2 The title of the "," Ms. Hu 2 The content of ",1585645673144,"mjmjmj");
SELECT * FROM myblog.users LIMIT 0,1000;
-- select username from users;
-- select * from  users where password like '%1%' order by id desc;
-- select * from blogs;
-- ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY 'password' PASSWORD EXPIRE NEVER;
-- ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY '11111111';
-- flush privileges
-- insert into blogs (title, content, createtime, author)values ('hhhhhh', 'jjhhhhh', 1585646800912, 'mjmjmj');

-- select username, realname from users where username='mjmjmj' and password='321654a.'

--  to update 
-- SET SQL_SAFE_UPDATES = 0;
-- update users set state = 0;
-- update users set username ='huhuhu' where id = '2';

--  Delete 
-- delete from blogs where id='1';

5.4 nodejs operation database

const mysql = require('mysql');

const con = mysql.createConnection({
    host: 'localhost',
    user: 'root',
    password: '11111111',
    port: '3306',
    database: 'myblog',
})
//  Start connecting 
con.connect()
//  perform sql
const sql = 'select * from users;';
con.query(sql, (err, result) => {
    if (err) {
        console.log(err);
        return;
    }
    console.log(result);
})
con.end();
const mysql = require('mysql');

const { MYSQL_CONF } = require("../conf/db");
//  Create linked objects 
const con = mysql.createConnection(MYSQL_CONF);
//  Establishing a connection 
con.connect();
//  Unified execution sql  Function of 
function exec(sql) {
    const promise = new Promise((resolve, reject) => {
        con.query(sql, (err, result) => {
            if (err) {
                reject(err);
                return
            }
            resolve(result)
        })
    })
    return promise;
}

con.end();
module.exports = {
    exec
}

6.2 Cookie Introduce

What is? cookie?
js How to operate cookie, How to view cookie?
server End operation cookie, Implement login authentication 、

characteristic :

  1. Maximum 5kb
  2. Cross domain not shared ,
  3. Structured data can be saved
  4. Send each time http request , The cookoie Send to cookie
  5. server The end can be modified cookie, And return it to the client
  6. The client can also use the js modify cookie, And return it to server End ( Limited )
  7. See which domain is requested , Which domain to request , Take which cookie
Inside the request header cookie

image.png

Local cache cookie

image.png

domin:cookie Domain name in effect
path: yes cookie Effective path

modify cookie

image.png
With localStorage , Local modification cookie It's not much

nodejs modify cookie
//  analysis  cookie
    req.cookie = {}
    const cookieStr = req.headers.cookie || ''  // k1=v1;k2=v2;k3=v3
    cookieStr.split(';').forEach(item => {
        if (!item) {
            return
        }
        const arr = item.split('=')
        const key = arr[0].trim()
        const val = arr[1].trim()
        req.cookie[key] = val
    })
nodejs setCookie
    //  Sign in 
    if (method === 'POST' && req.path === '/api/user/login') {
        const { username, password } = req?.body
        const result = login(username, password)
        return result.then(data => {
            if (data.username) {

                //  operation cookie
                res.setHeader('SetCookie', `username=${data.username}`)
                return new SuccessModel()
            }
            return new ErrorModel(' Login failed ')
        })
    }

6.4 cookie Make restrictions

Set up httpOnly

res.setHeader('SetCookie', `username=${data.username}; path=/; httpOnly`)
//  obtain  cookie  The expiration time of 
const getCookieExpires = () => {
    const d = new Date()
    d.setTime(d.getTime() + (24 * 60 * 60 * 1000))
    console.log('d.toGMTString() is ', d.toGMTString())
    return d.toGMTString()
}
    res.setHeader('Set-Cookie', `userid=${userId}; path=/; httpOnly; expires=${getCookieExpires()}`)

6.6 session

cookie in Will expose username, It's dangerous
useridsidconentid, Corresponding server End username.

  • session Is directly js Variable , Put it in nodejs In process memory ;
  • Too much memory , It's going to blow up the process space
  • Between multiple processes , Data can't be shared

6.8 redis

redis solve Multi process Can't communicate with each other session The problem of ( Squish , There is no data sharing between multiple processes .), Is the server side commonly used cache tool .

web server The most commonly used cache database , Data is stored in memory , comparison mysql Fast reading and writing , But it's more expensive , Power loss .

  • Separate services , And nodejs It's just a calling relationship between them . It's like mysql equally , So there's no crowding .
  • Multiple processes access the same redis. therefore session It's going to sync .
  • redis Scalable , Even if the number of users increases , That can also add machines , It can be expanded into clusters .

session High performance requirements , Because every time you send a request . It doesn't matter if you lose the power , Log in again . So it can't exist directly mysql in .

image.png

image.png

6.9

const redis = require('redis');
const { REDIS_CONF } = require('../conf/db');

//  Create client 
const redisClient = redis.createClient(REDIS_CONF);

redisClient.on('error', (error) => {
    console.log(error);
})

function set(key, val) {
    if (typeof val === "object") {
        val = JSON.stringify(val);
    }
    redisClient.set(key, val, redis.print);
}
function get(key) {
    const promise = new Promise((resolve, reject) => {
        redisClient.get(key, (err, val) => {
            if (err) {
                reject(err)
                return
            }
            if (val == null) {
                resolve(null);
                return
            }
            try {
                resolve(JSON.parse(val))
            } catch (ex) {
                resolve(val)
            }
            resolve(val);
        })
    });

    return promise;
}

module.exports = {
    set,
    get
}
set myname mj
get myname // mj
get * //  Get all key value
    //  obtain  session
    req.sessionId = userId
    get(req.sessionId).then(sessionData => {
        if (sessionData == null) {
            //  initialization  redis  Medium  session  value 
            set(req.sessionId, {})
            //  Set up  session
            req.session = {}
        } else {
            //  Set up  session
            req.session = sessionData
        }
        // console.log('req.session ', req.session)

        //  Handle  post data
        return getPostData(req)
    })
        .then(postData => {
        ......
  }

6.14 Why use nginx

Because of a service from the front end and nodejs The service from is not the same port , and cookie Cross domain not shared .
image.png

Use http-server Start a front-end service . Port set to 8001.
nodejs:8000 port

Everybody go to 8080 port .

6.15 High performance web The server nginx), Open source , free

If requested / root directory , request html, that ,nginx Go back straight back to html

If requested /api/blog/... Come first nginx port 8000, And then to node Port of service ,8001.

Agents that are not visible to clients , be called Reverse proxy

Use easyconnect Connect , go by the name of Forward agency , The client can control
image.png

image.png

image.png

  • Test if the configuration file format is correct : ngnix -t
  • start-up nginx restart nginx -s reload
  • stop it ngnix -s stop
sudo vi /usr/local/etc/nginx/nginx.conf

The main thing is to add the code , Then comment out some of the above .

location / {
    proxy_pass <http://localhost:8001>;
}
location /api/{
    proxy_pass <http://localhost:8000>;
    proxy_set_header Host $host;
} 

It's been a long time , Is to understand what is redis, What is? session, What is? ngnix, In the code is a match .

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