node.js database operations

node using MySQL 
        const HTTP = the require ( 'HTTP' ); 
        const MySQL = the require ( 'MySQL' ); 
        const URL = the require ( 'URL' ); 
        const FS = the require ( 'FS' ); 

        // 1. connection to database 
        the let DB = mysql.createConnection ({ 
            Host: 'localhost' , 
            User: 'the root' , 
            password: '' , 
            database: '' 
        }); 

        // connection pool resolve concurrency [problem] 
        / * the let DB = mysql.createPool ({  
            connerctionLimit:10, // default is 10
            Host: 'localhost',
            user: 'root',
            password:'',
            database:''
        });*/


        //查询
        db.query('SELECT * FORM user_Table',(err,data)=>{
            if(err){
                console.log('错了');
            }else{
                console.log(data);
            }
        });

        //2.配合http
        http.createServer((req,res)=>{
            const {pathname,query}  = url.parse(req.url,true);

            if(pathname === '/reg') {
                 //Parameters are correct 
                the let {username, password} = Query;
                 IF (username ||!! Password) { 
                    res.write ( 'user and password can not be empty' ); 
                    res.end (); 
                } the else  IF (username.length> 32 ) { 
                    res.write ( 'user name can not be greater than 32' ); 
                    res.end (); 
                } the else  IF (password.length> 32 ) { 
                    res.write ( 'the password is not greater than 32' ); 
                    res.end (); 
                } the else {
                    db.query(`SELECT ID FROM user_table  WHERE username='${username}'`,(err,data)=>{
                        if(err){
                            res.write('数据库有错');
                            res.end();
                        }else if(data.length>0){
                            res.write('用户名已存在')；
                            res.end();
                        }else{
                            db.query(`SELECT INFO user_table (username,password) VALUES('${username}','${password}')`,err=>{
                                 the elseIF (ERR) { 
                                    res.write ( 'wrong database' ); 
                                    res.end (); 
                                } the else { 
                                    res.write ( 'registration success' ); 
                                    res.end (); 
                                } 
                            }) 
                        } 
                    }) 
                } 

                // check username exists 

            } the else  iF (pathname === '/ Login' ) { 
                
            } { 
                fs.readFile ('www'+pathname,(err,buffer)=>{
                    if(err){
                        res.writeHeader(404);
                        res.write('no found');
                    }else{
                        res.write(buffer);
                    }
                    res.end();
                })
            }
        })


        3.异步模块（co-mysql）
        const co = require('co-mysql');
        let conn = mysql.createPool({
            host:'localhost' );,
            User: 'the root' , 
            password: '' , 
            Database: '' 
        }); 

        the let DB = CO.'s (Conn); 

        http.createServer (the async (REQ, RES) => { 
            const {pathname, Query}   = url.parse ( req.url, to true ); 

            iF (pathname === '/ REG' ) {
                 // parameters are correct 
                the let {username, password} = Query;
                 iF !! (|| username password) { 
                    res.write ( 'users and password can not be empty ' 
                    res.end ();
                } The else  IF (username.length> 32 ) { 
                    res.write ( 'User name can not be greater than 32' ); 
                    res.end (); 
                } the else  IF (password.length> 32 ) { 
                    res.write ( 'password can not be greater than 32 ' ); 
                    res.end (); 
                } the else {
                     the try { 
                        the let Data = db.query the await (the FROM `the SELECT ID user_table the WHERE username =' $ {username} ' `);
                         IF (data.length> 0 ) {
                            res.write ( 'User name already exists' ); 
                        } the else { 
                            the await db.query ( `the INFO user_table the SELECT (username, password) the VALUES ( '$ {username}', '{$ password}' )`); 
                            RES. Write ( 'registration success' ); 
                        } 
                    } the catch (ERR) { 
                        res.write ( ' wrong database ' ); 
                    } 
                    res.end (); 
                } 

                // check the user name exists 

            } the else  iF (pathname ===' / login '){
                
            }else{
                fs.readFile('www'+pathname,(err,buffer)=>{
                    if(err){
                        res.writeHeader(404);
                        res.write('no found');
                    }else{
                        res.write(buffer);
                    }
                    res.end();
                })
            }
        })