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js实现orm

2026-04-06 22:28:59JavaScript

使用 JavaScript 实现 ORM（对象关系映射）可以通过多种方式实现，以下是几种常见的方法和工具：

原生 JavaScript 实现 ORM

通过封装数据库操作，将数据库表映射为 JavaScript 对象。以下是一个简单的实现示例：

class ORM {
  constructor(db) {
    this.db = db;
  }

  async create(table, data) {
    const keys = Object.keys(data).join(', ');
    const values = Object.values(data).map(v => `'${v}'`).join(', ');
    const query = `INSERT INTO ${table} (${keys}) VALUES (${values})`;
    return this.db.query(query);
  }

  async find(table, conditions = {}) {
    let whereClause = '';
    if (Object.keys(conditions).length > 0) {
      const conditionsStr = Object.entries(conditions)
        .map(([key, val]) => `${key} = '${val}'`)
        .join(' AND ');
      whereClause = `WHERE ${conditionsStr}`;
    }
    const query = `SELECT * FROM ${table} ${whereClause}`;
    return this.db.query(query);
  }

  async update(table, conditions, data) {
    const setClause = Object.entries(data)
      .map(([key, val]) => `${key} = '${val}'`)
      .join(', ');
    const whereClause = Object.entries(conditions)
      .map(([key, val]) => `${key} = '${val}'`)
      .join(' AND ');
    const query = `UPDATE ${table} SET ${setClause} WHERE ${whereClause}`;
    return this.db.query(query);
  }

  async delete(table, conditions) {
    const whereClause = Object.entries(conditions)
      .map(([key, val]) => `${key} = '${val}'`)
      .join(' AND ');
    const query = `DELETE FROM ${table} WHERE ${whereClause}`;
    return this.db.query(query);
  }
}

使用现有 ORM 库

以下是一些流行的 JavaScript ORM 库，可以简化数据库操作：

js实现orm

Sequelize

支持多种数据库（如 MySQL、PostgreSQL、SQLite），提供模型定义、关联和查询功能。

const { Sequelize, DataTypes } = require('sequelize');
const sequelize = new Sequelize('database', 'username', 'password', {
  dialect: 'mysql',
});

const User = sequelize.define('User', {
  name: DataTypes.STRING,
  age: DataTypes.INTEGER,
});

async function main() {
  await sequelize.sync();
  const user = await User.create({ name: 'John', age: 30 });
  const users = await User.findAll();
}

TypeORM

支持 TypeScript 和 JavaScript，提供装饰器语法和多种数据库支持。

js实现orm

import { Entity, PrimaryGeneratedColumn, Column, createConnection } from 'typeorm';

@Entity()
class User {
  @PrimaryGeneratedColumn()
  id: number;

  @Column()
  name: string;

  @Column()
  age: number;
}

async function main() {
  const connection = await createConnection({
    type: 'mysql',
    database: 'test',
  });
  const user = new User();
  user.name = 'John';
  user.age = 30;
  await connection.manager.save(user);
}

Prisma

现代 ORM 工具，支持自动生成类型安全的查询。

const { PrismaClient } = require('@prisma/client');
const prisma = new PrismaClient();

async function main() {
  const user = await prisma.user.create({
    data: { name: 'John', age: 30 },
  });
  const users = await prisma.user.findMany();
}

自定义 ORM 的高级功能

如果需要更复杂的功能（如关联、事务），可以扩展原生实现：

class AdvancedORM extends ORM {
  async findWithRelations(table, conditions, relations) {
    const whereClause = Object.entries(conditions)
      .map(([key, val]) => `${key} = '${val}'`)
      .join(' AND ');
    const joinClauses = relations.map(rel => `JOIN ${rel} ON ...`);
    const query = `SELECT * FROM ${table} ${joinClauses.join(' ')} ${whereClause}`;
    return this.db.query(query);
  }

  async transaction(callback) {
    await this.db.query('BEGIN');
    try {
      await callback();
      await this.db.query('COMMIT');
    } catch (error) {
      await this.db.query('ROLLBACK');
      throw error;
    }
  }
}