This article takes you nodejs from introduction to mastery

Posted by Amanda1998 on Mon, 03 Jan 2022 12:54:54 +0100

"The ancients' knowledge is weak, but their Kung Fu can only be achieved when they are young and old."

One article takes you from the introduction to the mastery of nodejs. In fact, the cost of learning nodejs is not so high. You only need this article from brother feitu. Ten minutes will take you from the introduction to the mastery. I hope if you think this article can bring you some help, I hope to give brother feitu a key three times to express support. Thank you~

catalogue

1, Installation and simple use

2, Custom module

3, node built-in module

4, npm command line tool

5, Install the mime module and use

Vi. module for managing npm source

7, Switch nodejs version using NVM

8, Automatic restart and date processing module

9, Web crawler

10, Database operation

Xi. Release of customized module package

12, Express framework

13, KOA2 framework

1, Installation and simple use

# Enter node environment
node

# Output hello world
console.log('hello world')

2, Custom module

  • A custom module is to define its own methods and then introduce them where needed
  • We create a say JS file, write the following
  • command
function say(){
	console.log("hello world!");
}

exports.say = say;
  • When you need to use this say method in a file
  • You can import using the following methods
  • command
var res = require("./say");
res.say();

3, node built-in module

  • os system module
var os = require("os");

Line feed: os.EOL
 Host name: os.hostname();
Operating system: os.type();
Operating platform: os.platform();
Total memory(byte): os.totalmem();
idle memory(byte): os.freemem();
  • path module
var path = require("path");

var filepath ="https://www.xxxx.cn/wechat/wechatpay.php";

File name: path.basename(filepath);
Directory name: path.dirname(filepath);
  • url module
var url = require("url");

var data ="https://www.jiangliang738.cn?name=eden&age=24";

url.parse(data);

Become object: $info = url.parse(data,true);
Get parameters: $info.query
  • fs file module
var fs = require("fs");

fs.writeFile(Path and file name, "utf8", function(err, data){
	if(!err){
		console.log(data);
	}
});
  • http module 
var http = require("http");

#Create web server
var server = http.createServer();

#Listening request
server.on('request',function(req,res){
	console.log("Request received"+req.url);
	res.setHeader("Content-Type","text/html;charset=utf-8");
	res.write("Hello nodejs");
	res.end();
})

#Start service
server.listen(8080,function(){
	console.log("Service started successfully");
})

4, npm command line tool

  • npm is a command-line tool used to manage modules. You can download and import any modules you need
  • Module website: https://www.npmjs.com
  • Downloading nodejs will automatically install the npm tool
  • npm has some common commands, as follows
  • command
npm -v # View npm version
npm list # See which modules are installed
npm init -y # initialization
npm install [modular] # Installation module
npm uninstall [modular] # Uninstall module

5, Install the mime module and use

  • For example, we need to install the mime module
  • command
npm -i mime [-g]
  • Detailed explanation of installation parameters
  • -g this module can be run on the command line
  • --save records the modules required by the production environment
  • --Save dev records the modules required by the development environment
  • Using the mime module
//Introduction module
var mime = require("mime");
//Determine file type
var img = "xxxx.png";

console.log(mime.getType(img));
console.log(mime.getExtension("image/png"));

Vi. module for managing npm source

  • Because npm is used to download and manage modules
  • npm must be active. If the source address is abroad, you will find that the download is very slow. At this time, we have to switch the source
  • The module that manages npm sources is called nrm
  • command
# Install nrm
npm install nrm [-g]

# View source address list
nrm ls

# Switch address
nrm use server name

# velocity measurement
nrm test

7, Switch nodejs version using NVM

  • To manage the version of nodejs, you need to use the nvm service
  • nvm service needs to be installed first
  • nvm has many common commands as follows
  • command
#View version
nvm version

#Install the latest version
nvm install latest

nvm install Version number

nvm uninstall Version number

# View all nodejs versions
nvm list

#Switch to new version
nvm use Version number

8, Automatic restart and date processing module

  • Our common modules are automatic restart and date processing

  • If we want to modify mime Any content in JS can see the effect immediately, instead of taking effect after restarting manually

  • command

# Install the automatic restart module
npm install nodemon [--save-dev -g]

# use
nodemon mime.js
# Installation time module
npm install moment

# use
var moment = require('moment');
console.log( moment().format() );

9, Web crawler

  • node can be crawled, and the cherio module needs to be used
  • This module can be understood as jq of node version, which is used to obtain web page data
  • command
# install
npm i cheerio
# Basic use of this module
var http = require("http");

http.get("website", function(req,res){
	#Used to save web page data
	var html='';

	req.on("data",function(data){
		html +=data;
	})

	req.on("end",function(){
		getTittle(html)
	})
})

function getTittle(html){
	#Introduction of crawler module
	const cheerio = require("cheerio");

	#Encapsulate the obtained html code into a $object
	const $ = cheerio.load(html,{decodeEntities:false});

	#Matching data
	$('selector').each(function(index,item){
		console.log($(item).html());
	});
}

10, Database operation

  • node can be listed as a back-end language because it can manipulate databases
  • To operate the database, we need to install the mysql module. For more information, please refer to the document: https://www.npmjs.com/package/mysql
  • command
# Installation module
npm i mysql
# Basic use
var mysql = require('mysql');
var connection = mysql.createConnection({
  host : 'localhost', # Database host
  user : 'me', # Database account
  password : 'secret', # Database password
  database : 'my_db' # database
});

connection.connect();

connection.query('mysql sentence', function (error, results, fields) {
  if (error) throw error;
  console.log('The solution is: ', results[0].solution);
});

connection.end();

Xi. Release of customized module package

  • In the above, we all use other people's modules downloaded by npm, so how to define our own package and put it on the website for others to use
  • We need to encapsulate our package and upload it to https://www.npmjs.com Website, package management, you can let others download
  • First of all, we need to register our own account on this website. We need to have our own account
  • command
# Create a local folder and initialize it
npm init -y

# Configure package JSON parameter
{
  "name": "mydemo", # Project name, such as mysql above
  "version": "1.0.0",
  "description": "this is a package", # Project description
  "main": "index.js",
  "scripts": {
    "test" : "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": ["nodejs", "php"],
  "author": "autofelix",
  "license": "ISC"
}

# In index JS package code
function say(){
	console.log("hello npm");
}

exports.say = say;

# nrm can only be published after switching to a foreign server
nrm ls

nrm use npm

# Log in to your account and enter your account, password and email
npm login

# Upload to warehouse
npm publish

12, Express framework

  • This is a node module. This module is used to develop websites, making website development easy
  • command
# initialization
npm init -y

# Install the frame module
npm install express
  • Basic use
#Introduction module
var express = require("express");

#Create server
var app = express();

#Listening request
app.get("/", function(req, res){
	//end() response string (garbled)
	//send() response string (automatic recognition)
	//render() response string (automatic recognition, specifying the string in the file)
});

#Start service
app.listen(8080,function(){
	console.log("Start successful");
})
# Install template engine
npm install art-template
npm install express-art-template
  • Advanced use
  • Because the render method calls the views under the root directory by default, you need to create the directory manually
#Introduction module
var express = require("express");

#Create server
var app = express();

#Configuration engine
app.engine("html", require('express-art-template'));

#Listening request
app.get("/", function(req,res){
	//end() response string (garbled)
	//send() response string (automatic recognition)
	//render() response string (automatic recognition, specifying the string in the file)

	res.render("test.html"{
		[Parameter 1]: [Value 1],
		[Parameter 2]: [Value 2],
		[Parameter 3]: [
			{id:1,title:"Title 1"},
			{id:2,title:"Title 2"},
			{id:3,title:"Title 3"}
		],
	})
});

#Start service
app.listen(8080,function(){
	console.log("Start successful");
})
  • Routing in framework
#get route
app.get(Request path, callback function);

#post routing
app.post(Request path, callback function);

#Arbitrary request
app.all(Request path, callback function);
app.use(Request path, callback function);
  • Static resource hosting
#Allows files in the specified directory to be accessed externally
#Syntax: Express Static ("directory name")

app.use("/public",express.static("public"));
  • Template loop syntax
{{each orders as order index}}

{{/each}}

13, KOA2 framework

# Installing the frame generator koa generator
npm install koa-generator -g

# Generating stu projects through koa generator
koa2 stu

# Install framework dependent framework (default, module engine, database, etc.)
cd stu && npm install
npm install art-template koa-art-template mysql

Topics: node.js Database crawler

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