node持久化的几种方式

• 文件系统 csv Comma-Separated Values 逗号分割 xx;xx json 对象序列化 {aa:'11'} => "{aa:'11'}"
• 数据库
  1. mysql 关系型
  2. mongodb 文档型
  3. redis 键值关系

文件系统

//通过本地json对象序列化存储与读取
const fs = require("fs");

function get(key) {
  fs.readFile("./db.json", (err, data) => {
    const json = JSON.parse(data);
    console.log(json[key]);
  });
}
function set(key, value) {
  fs.readFile("./db.json", (err, data) => {
    // 可能是空文件，则设置为空对象
    const json = data ? JSON.parse(data) : {};
    json[key] = value; // 设置值
    // 重新写入文件
    fs.writeFile("./db.json", JSON.stringify(json), err => {
      if (err) {
        console.log(err);
      }
      console.log("写入成功！");
    });
  });
}

// 命令行接口部分
const readline = require("readline");
const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout
});

rl.on("line", function(input) {
  const [op, key, value] = input.split(" ");

  if (op === 'get') {
    get(key)
  } else if (op === 'set') {
    set(key, value)
  } else if(op === 'quit'){
    rl.close();
  }else {
    console.log('没有该操作');
  }
});

rl.on("close", function() {
  console.log("程序结束");
  process.exit(0);
});

//测试 启动后命令行输入
set aa bb
//写入成功！
get aa
//bb

mysql

//安装
npm i sequelize mysql2 -S
//使用：
(async () => {
    const mysql = require('mysql2/promise')

    // 连接配置
    const cfg = {
        host: "localhost",
        user: "root",
        password: "xxx", // 修改为你的密码
        database: "xxxx" // 请确保数据库存在
    }

    const connection = await mysql.createConnection(cfg)

    let ret = await connection.execute(`
        CREATE TABLE IF NOT EXISTS test (
            id INT NOT NULL AUTO_INCREMENT,
            message VARCHAR(45) NULL,
        PRIMARY KEY (id))
    `)
    console.log('create', ret)

    ret = await connection.execute(`
            INSERT INTO test(message)
            VALUES(?)
    `, ['ABC'])
    console.log('insert:', ret)


    ret = await connection.execute(`
            SELECT * FROM test
    `)
    console.log(JSON.stringify(ret[0]))
    // console.log(ret[1])

    connection.end()

})()    

基于Promise的ORM （object relation mapping）对象关系映射 - Sequelize

//安装
npm i sequelize sequelize -S
//使用：
(async () => {

    // 1:N关系
    const Sequelize = require("sequelize");

    // 建立连接
    const sequelize = new Sequelize("kaikeba", "root", "xxxx", {
        host: "xxxxx",
        dialect: "mysql",
    });

    const Fruit = sequelize.define("fruit", { name: Sequelize.STRING });
    const Category = sequelize.define("category", { name: Sequelize.STRING });
    Fruit.FruitCategory = Fruit.belongsToMany(Category, {
        through: "FruitCategory"
    });

    // 插入测试数据
    sequelize.sync({ force: true }).then(async () => {
        await Fruit.create(
            {
                name: "香蕉",
                categories: [{ id: 1, name: "热带" }, { id: 2, name: "温带" }]
            },
            {
                include: [Fruit.FruitCategory]
            }
        );
        // 多对多联合查询
        const fruit = await Fruit.findOne({
            where: { name: "香蕉" }, // 通过through指定条件、字段等
            include: [{ model: Category, through: { attributes: ['id', 'name'] } }]
        });
    })

})()

常用创建命令

//避免生成多余时间字段
timestamps: false

//解决数据库移植唯一问题
id: { 
    type: Sequelize.DataTypes.UUID, 
    defaultValue: Sequelize.DataTypes.UUIDV1,
    primaryKey: true
},

一对多 多对一关系

const Sequelize = require('sequelize');
module.exports.initModel = async sequelize => {
    // 创建user表
  const User = sequelize.define('user', { name: Sequelize.STRING });
    // 创建商品表
  const Product = sequelize.define('product', { title: Sequelize.STRING });
  Product.belongsTo(User); // 1端建立关系
  User.hasMany(Product); // N端建立关系
  
  return { User, Product }
}