How to build a simple server using nodejs

Use nodejs to build a simple server

Nodejs advantages: high performance (reading and writing files) and strong data manipulation capabilities
Official website: www.nodejs.org
Verify whether the installation is successful: cmd command Enter node -v in the line. If the version number is displayed, the installation is successful.

[Common commands]

Switch drive letter d:
Enter the folder cd nodejs
Return to the previous directory cd..
Clear screen cls
Display directory dir
Copy file name, select right-click--Copy
Historical operation up arrow
Execute file node file name (in the file folder directory)
Stop the command line ctrl+c

Nodejs can use ECMAScript, read and write files, database operations, and build servers
What nodejs cannot do is: DOM, BOM

Use node to build A server:

//1、引入模块  使用的http服务协议是RFC2616  nodejs的作者已经写好了，直接引入就行
var http = require('http');
//引入文件读写模块fs
var fs = require('fs');
//2、创建服务器    函数的参数req是发送给服务器的请求，res是服务器的相应
var httpObj = http.createServer(function(req,res){
    //编写url  其中index.html是要服务器读取的文件
    var url = req.url=='/'?'index.html':req.url;
    //开始文件读取，参数分别是完整的url 编码 和读取完毕执行的函数，注意前后台编码需要一致
    fs.readFile('www/'+url,'utf-8',function(err,data){
        //res.write服务器的相应，当成功的时候，服务器会传输一个data数据，相应结束需要end
        if(err){ 
            res.write('404,您访问的页面不存在');
            res.end();    
        }else{
            res.write(data);
            res.end();    
        }
    });
});
//监听端口
httpObj.listen(80);

Use nodejs to write a sql statement

//和搭建服务器一样，需要先引入模块，mysqle是外生的模块（提前在node中下载），MySQL模块会告诉服务器我们需要add还是get
//1、引入模块，这里多引入了一个mysql模块
var http = require('http');
var fs = require('fs');
var mysql = require('mysql');
//2、连接服务器使用createServer，同样参数也是req和res
var httpObj = http.createServer(function(req,res){
    var url = req.url=='/'?'index.html':req.url;
    console.log(url);
    //给前端提供一个json 写前端接口
    //这里多了地址、用户名、密码和数据库
    if(url.split('?')[0]=='/article'){
        //console.log('我要给前端数据接口');
        //1.建立连接
        var db = mysql.createConnection({
            //地址
            host:'localhost',
            //用户名
            user:'root',
            //密码
            password:'',
            //数据库
            database:'study'
        });
        //3、编写sql语句，就是在想请求的时候告诉服务器我们需要add还是get
        var sql = 'SELECT * FROM user';
        //3.执行sql返回结果
        db.query(sql,function(err,data){
            if(err){
                console.log('失败');
            }else{
                //console.log(data[0].username);
                //console.log(JSON.stringify(data));
                res.write(JSON.stringify(data));
                res.end();
            }
        });
    }else{
        //读取页面
        fs.readFile('www/'+url,'utf-8',function(err,data){
            if(err){ 
                res.write('404,您访问的页面不存在');
                res.end();    
            }else{
                res.write(data);
                res.end();    
            }
        });
    }
});
//4、监听端口
httpObj.listen(3000);

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