nodejs前后端的数据交互

数据流向一般是：前端请求 ---->后端数据校验 ---->查询数据库 ---->响应前端

基本的数据库sql(结构化查询语句)一般涉及增删改查四大操作，具体如下：

1. 增
   INSERT INTO 表(字段列表) VALUES(值列表)

INSERT INTO user_table(ID,name,gender,chinese,math,english) VALUES(0,"张三","男",20,30,50)

2. 删
   DELETE FROM 表 WHERE 条件

DELETE FROM user_table WHERE ID=1

3.改
UPDATE 表 SET 字段1=值1,字段2=值2 WHERE 条件

UPDATE user_table SET chinese=20 WHERE ID=1

4. 查
   SELECT 字段1,字段2 FROM 表 WHERE 条件

SELECT chinsese FROM user_table WHERE ID=1

前后端配合完成简单注册和登陆的数据交互代码如下：

1. 前端代码：

    
    
    
    
    
    


    用户名：

    密码：

    注册
    登陆

2. 后端代码

const http = require("http");
const fs = require("fs");
const mysql = require("mysql");
const url = require("url");
const zlib = require("zlib");
const crypto = require("crypto");

let key = "1234656";
function md5(str){
    let obj = crypto.createHash("md5");
    obj.update(str);
    return obj.digest("hex");
}
function md5_2(str){
    return md5(md5(str+key));
}
//创建数据库的连接
let db = mysql.createPool({host: "localhost", port: "3306", user: "root", password: "cf540294", database: "user"})
//创建服务
let server = http.createServer((req,res)=>{
    let {pathname,query} = url.parse(req.url,true);
    let {
        username,
        password
    } = query;
    switch(pathname){
        case "/reg":
            //对数据进行校验
            if(!username){
                res.write('{"err":1,"msg":"username can\'t be empty"}');
                res.end();
            }else if(!password){
                res.write('{"err":1,"msg":"password can\'t be empty"}');
                res.end();
            }else if(!/^\w{4,16}$/.test(username)){
                res.write('{"err":1,"msg":"username is invalid"}');
                res.end();
            }else if(/['|"]/.test(password)){
                res.write('{"err":1,"msg":"password is invalid"}');
                res.end();
            }else{
                //写入数据库之前先判断用户明是否存在
                db.query(`SELECT * FROM user_table WHERE username='${username}'`,(err,data)=>{
                    if(err){
                        res.write('{"err":1,"msg":"database error"}');
                        res.end();
                    }else{
                        if(data.length>0){
                            res.write('{"err":1,"msg":"the username is exists"}');
                            res.end();
                        }else{
                            db.query(`INSERT INTO user_table (id,username,password) VALUES(0,'${username}','${md5_2(password)}')`, (err, data) => {
                                if(err){
                                    res.write('{"err":1,"msg":"database error"}');
                                    res.end();
                                }else{
                                    res.write('{"err":0,"msg":"success"}')
                                    res.end();
                                }
                            })
                        }
                    }
                })
            }
            break;
        case "/login":
            //对数据进行校验
            if (!username) {
                res.write('{"err":1,"msg":"username can\'t be empty"}');
                res.end();
            } else if (!password) {
                res.write('{"err":1,"msg":"password can\'t be empty"}');
                res.end();
            } else if (!/^\w{4,16}$/.test(username)) {
                res.write('{"err":1,"msg":"username is invalid"}');
                res.end();
            } else if (/['|"]/.test(password)) {
                res.write('{"err":1,"msg":"password is invalid"}');
                res.end();
            } else {
                //写入数据库之前先判断用户明是否存在
                db.query(`SELECT * FROM user_table WHERE username='${username}'`, (err, data) => {
                    if (err) {
                        res.write('{"err":1,"msg":"database error"}');
                        res.end();
                    }else if(data.length == 0){
                        res.write('{"err":1,"msg":"the username is not exists"}');
                        res.end();
                    }else if(data[0].password != md5_2(password)){
                        res.write('{"err":1,"msg":"the username or password is incorrect"}');
                        res.end();
                    }else{
                        res.write('{"err":0,"msg":"success"}');
                        res.end();
                    }
                })
            }
            break;
        default:
            let rs = fs.createReadStream(`www${pathname}`);
            let gz = zlib.createGzip();
            res.setHeader("content-encoding","gzip");
            rs.pipe(gz).pipe(res);
            rs.on("error",err=>{
                res.writeHeader(404);
                res.write("Not Found");
                res.end();
            });
            break;
    }
})
// 监听端口
server.listen(8080);