What are the official modules of nodejs?

Nodejs official modules include: 1. path module, used to process file paths; 2. until module; 3. fs module, API of file operating system; 4. events module; 5. http module; 6. jade module; 7. Express module.

The operating environment of this tutorial: windows7 system, nodejs version 12.19.0, Dell G3 computer.

Nodejs built-in modules refer to the beauty provided in addition to the default syntax. No need to download, they can be imported directly. Just write the name.

nodejs built-in module:

1. Path module:

is used to process file paths .

path.normalize(路径解析，得到规范路径)；
path.join(路径合并)；
path.resolve（获取绝对路径）；
path.relative(获取相对路径)。
......

2. Until module:

Make up for the lack of js functions and add new APIs.

util.format(格式化输出字符串);
util.isArray(检查是否为数组);
util.RegExp(是不是正则);
util.isDate(是不是日期型);
util.inherits(child,parent)实现继承；

3. fs module:

API of file operating system

fs.readFile(filename,[options],callback); 读取文件。
fs.writeFile(filename,data,[options],callback);写文件。
fs.appendFile(filename,data,[options],callback);以追加的方式写文件。
fs.open(filename,flags,[mode],callback); 打开文件。
filename:文件名，必须。
data：写入的数据或者buffer流。
flags:操作标识，打开方式，r w。
[options]：指定权限，读、写、执行。是否可续写。
callback：读取文件后的回调函数。function（err，data）;
fs.mkdir(path,[mode],callback);创建目录。
fs.readdir(path,callback);读取目录。
fs.exists(path,callback);查看文件与目录是否存在。
fs.utimes(path,atime,mtime,callback);修改文件的访问时间和修改时间。
fs.rename(oldfilename,newfilename,callback);重命名文件名或者目录。
fs.rmdir(path,callback);删除空目录。
path：被创建目录的完整路径以及目录名。
[mode]:目录权限，默认0777（可读可写可执行）。
atime:新的访问时间。
ctime：新的修改时间。
oldfilename、newfilename  旧名字和新名字。
callback：创建完目录后的回调函数。

4. events module

events module only provides one object: events.EventEmitter.

[The core of EventEmitter is the encapsulation of event triggering and event listener functions. 】

Each event of EventEmitter consists of an event name and several parameters. The event name is a string, which usually expresses certain semantics. For each event, EventEmitter supports several event listeners. When an event is triggered, the event listeners registered to this event are called in turn, and the event parameters are passed as callback function parameters.

5. http module

http.createServer(function(){});创建服务器。
http.get('路径',callback);发送get请求。
http.request(options,callback);发送请求。
options：options是一个类似关联数组的对象，表示请求的参数，callback作为回调函数，需要传递一个参数。
options常用的参数有host、port（默认为80）、method（默认为GET）、path（请求的相对于根的路径，默认是“/”。

get:

var http=require("http");
 var options={
    hostname:"cn.bing.com",
    port:80
}
 
var req=http.request(options,function(res){
    res.setEncoding("utf-8");
    res.on("data",function(chunk){
        console.log(chunk.toString())
    });
    console.log(res.statusCode);
});
req.on("error",function(err){
    console.log(err.message);
});
req.end();

post:

var http=require("http");
var querystring=require("querystring");
 
var postData=querystring.stringify({
    "content":"我真的只是测试一下",
    "mid":8837
});
 
var options={
    hostname:"www.imooc.com",
    port:80,
    path:"/course/document",
    method:"POST",
    headers:{
        "Accept":"application/json, text/JavaScript, */*; q=0.01",
        "Accept-Encoding":"gzip, deflate",
        "Accept-Language":"zh-CN,zh;q=0.8",
        "Connection":"keep-alive",
        "Content-Length":postData.length,
        "Content-Type":"application/x-www-form-urlencoded; charset=UTF-8",
        "Cookie":"imooc_uuid=6cc9e8d5-424a-4861-9f7d-9cbcfbe4c6ae; imooc_isnew_ct=1460873157; loginstate=1;
         apsid=IzZDJiMGU0OTMyNTE0ZGFhZDAzZDNhZTAyZDg2ZmQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
         AAAAAAAAAAAAAAAAAAAAAAAAAAAAAMjkyOTk0AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
         AAAAAAAAAAAAAAAAAAAAAAAAAAAAAGNmNmFhMmVhMTYwNzRmMjczNjdmZWUyNDg1ZTZkMGM1BwhXVwcIV1c%3DMD;
          phpSESSID=thh4bfrl1t7qre9tr56m32tbv0; 
          Hm_lvt_f0cfcccd7b1393990c78efdeebff3968=1467635471,1467653719,1467654690,1467654957;
           Hm_lpvt_f0cfcccd7b1393990c78efdeebff3968=1467655022; imooc_isnew=2;
            cvde=577a9e57ce250-34",
        "Host":"www.imooc.com",
        "Origin":"http://www.imooc.com",
        "Referer":"http://www.imooc.com/video/8837",
        "User-Agent":"Mozilla/5.0 (Windows NT 10.0; WOW64) 
        AppleWebKit/537.36 (Khtml, like Gecko) Chrome/53.0.2763.0 Safari/537.36",
        "X-Requested-With":"XMLHttpRequest",
    }
}
 
var req=http.request(options,function(res){
    res.on("data",function(chunk){
        console.log(chunk);
    });
    res.on("end",function(){
        console.log("评论完毕！");
    });
    console.log(res.statusCode);
});
 
req.on("error",function(err){
    console.log(err.message);
})
req.write(postData);
req.end();

6. jade module

jade is a high-performance, concise and easy-to-understand template engine. HTML files can be written through jade.

jade is similar to a language for quickly writing HTML, and the suffix of the written file is .jade.

7. Express module

Express is a nodejs web open source framework, used to quickly build web projects. It mainly integrates the creation of web http servers, static text management, server URL address request processing, get and post request processing and distribution, session processing and other functions.

Usage method, open the path of the web project you want to create in cmd. Then enter

Express appname

to create a web project named appname.

[Recommended learning: "nodejs tutorial"]

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