Preliminary node.js

Node.js Introduction

Node.js was born in 2009, Node.js uses language written in C ++, is a Javascript runtime environment. Node.js is a JavaScript runtime environment Chrome V8 engine, allowing JavaScript to run out of the browser, you can use the JavaScript language to write server-side code.

Install Node.js

Node.js official website to download the stable version, node version is stable version even-odd version of a non-stable version.

mac mounted directly or brew to install
After installation is automatically installed Node.js NPM (Node Package Manager): package management tools;
To see if the installation is complete, and view node version number by instruction node -v; npm -v to see npm version.

Use Node.js to achieve the first server

Initial feelings Node.js

//引入http模块
let http = require("http");
//创建一个服务器
let serve = http.createServer((req,res)=>{
    console.log("hello");
    res.end("hello world");
})
//设置端口号
serve.listen(3000);

Google Chrome default non-secure port list, try to avoid the following ports.

1, // tcpmux
7, // echo
9, // discard
11, // systat
13, // daytime
15, // netstat
17, // qotd
19, // chargen
20, // ftp data
21, // ftp access
22, // ssh
23, // telnet
25, // smtp
37, // time
42, // name
43, // nicname
53, // domain
77, // priv-rjs
79, // finger
87, // ttylink
95, // supdup
101, // hostriame
102, // iso-tsap
103, // gppitnp
104, // acr-nema
109, // pop2
110, // pop3
111, // sunrpc
113, // auth
115, // sftp
117, // uucp-path
119, // nntp
123, // NTP
135, // loc-srv /epmap
139, // netbios
143, // imap2
179, // BGP
389, // ldap
465, // smtp+ssl
512, // print / exec
513, // login
514, // shell
515, // printer
526, // tempo
530, // courier
531, // chat
532, // netnews
540, // uucp
556, // remotefs
563, // nntp+ssl
587, // stmp?
601, // ??
636, // ldap+ssl
993, // ldap+ssl
995, // pop3+ssl
2049, // nfs
3659, // apple-sasl / PasswordServer
4045, // lockd
6000, // X11
6665, // Alternate IRC [Apple addition]
6666, // Alternate IRC [Apple addition]
6667, // Standard IRC [Apple addition]
6668, // Alternate IRC [Apple addition]

6669, // Alternate IRC [Apple addition]

Modular

First, why would modular

Is to achieve a simple page interaction logic, a few words that JavaScript early stages of development, now with the expanding front-end code

This time targeting the embedded JavaScript as scripting language shaken, JavaScript does not provide any significant help for the organization code, JavaScript code is very simple organizational norms is not sufficient to manage such a large-scale code;

Two, Node.js specification of modular commonjs

CommonJS JS performance is to make your specifications, because there is no js function modules so CommonJS came into being, it wants js can run anywhere, not just browsers.

1. Create a custom module
- The introduction of a document in the form of module
  
  home.js executable file
```
//通过require来引入
require("./aModule"); //注意一定要有"./"，文件后缀可加可不加。
```
  amodule.js file
```
console.log("我是amodule模块111");
```
- The introduction of a folder in the form of modules
  - home.js executable file
```
require("./aModuledir"); //必须加"./"
```
  aModuleDir in the index.js file will automatically find index.js file folder under execution
```
console.log("我是aModule模块文件夹");
```
  - Of course, you can configure the default boot file, the new package.json within the folder to specify the executable file
```
{
  "name":"aModule",
  "version":"1.0.0",
  "main":"test.js"
}
```

Custom module export demand

Export by module.exports; ___dirname, __filename

module.exports = {
    a:"我是a的值",
    b(){
        console.log("我是导出的b函数");
    }
}

The introduction of the export file

let mymodule = require("bModule");
console.log(mymodule.a);
mymodule.b();

Or derived by exports

exports.fn = function(){
    console.log("我是fn函数");  
}

Importing files

let myfn = require("bModule").fn;
myfn();
// 或者 通过解构赋值 
let { fn } = require("bModule");
fn();

Module loading priority, then the first file directory;

2, built-in module;

nodejs built-in module has: Buffer, C / C ++ Addons, Child Processes, Cluster, Console, Cr

ypto，Debugger，DNS，Domain，Errors，Events，File System，

Globals, HTTP, HTTPS, Modules, Net, OS, Path, Process, P unycode, Query Strings, Readline, REPL, Stream, String De coder, Timers, TLS / SSL, TTY, UDP / Datagram, URL, Utilities, V8, VM, ZLIB; no need to install built-in module, the module needs to be installed externally;

npm package manager

Address NPM (Node Package Manager) is the official website of npm official website

npm common commands;
- npm init: create a boot file package.json
- npm help (npm -h): View npm help
- npm version (npm -v): View npm version;
- npm search: Find
- npm install (npm i): installation default in the current directory, if not node_modules will create folders;
  - npm install module_name -S or --save i.e. npm install module_name --save write dependencies
  - npm install module_name -D or -save-dev i.e. npm install module_name --save-dev written devDependencies
  - npm install module_name -g global mount (using command line)
  - Specifies the version of the installation module npm i module_name @ 1.0 by the "@" symbol specified;
- npm update(npm -up)：更新
- npm remove or npm uninstall: Delete
- See npm root path of the current package is installed or mounted to view the global path through npm root -g;

fs module

fs is the file operating module, all file operations are divided synchronous and asynchronous, characterized by the synchronization will add "Sync" as: reading files asynchronously "readFile", reads the file sync "readFileSync";

File Operations

File reads:

Asynchronous read

let fs = require("fs");
fs.readFile("1.txt",(err,data)=>{
    if(err){
        return console.log(err);
    }
    console.log(data.toString());
})

Synchronous read the file

let fs = require("fs");
let res = fs.readFileSync("1.txt");
console.log(res.toString());

File write:

let fs = require("fs");
//flag配置  "a":追加写入，"w":写入，"r":读取
fs.writeFile("2.txt","我是要写入的内容",{flag:"w"},err=>{
    if(err){
        return console.log(err);
    }
    console.log("写入成功");   
})

File deletion

fs.unlink("2.txt",err=>{
    if(err){
        return console.log(err);
    }
    console.log("删除成功");
})

Copy files

First read the file and then write to the file

function mycopy(src,dest){
   fs.writeFileSync(dest,fs.readFileSync(src));
}
mycopy("1.txt","4.txt");

Modify the file name, directory can also be operated by rename

fs.rename("1.txt","5.txt",function (err) {
    if(err){
        console.log(err);
    }else{
        console.log("修改成功");
    }
});

Determine whether a file exists

fs.exists("4.txt",function (exists) {
    console.log(exists);
})

buffer buffer

the creation of buffer
- Created directly
- Array creation
- Create a string
- Garbage processing
- buffer conversion tostring

stream flow

stream stream: the stream data processing inseparable
- Principle stream
- Obtaining stream data
  - pipe
  - data
  - end
- implemented method of copy stream
- Implemented method of loading a flow view

to sum up

Installation and use of nodejs
Server and client
Modular commonjs
Use fs module (file operations and directory operations)
stream
buffer