What is an ORM ?

ORM Stands For Object Relational Mapping Used To Convert Data Between Incompatible Type System Using Object Oriented Programming Languages Like JavaScript, TypeScript, Python

Popular ORM's

• JavaScript
  • Sequelize
  • Prisma
• TypeScript
  • TypeORM
  • Mikro-ORM
• Python
  • SQLAlchemy
  • Django ORM

Why TypeORM

If You Know Me, I Am a Big Fan Of TypeScript And I Like Both Mikro-ORM And TypeORM But The Thing With TypeORM That It Is More Of Like TypeScript Syntax. Basically I Like TypeORM Syntax Than Mikro-ORM

Setting Up TypeORM

• Requirements
  • Node.js
  • NPM

Creating A Basic Node.js App

# NPM
npm init
# Yarn
yarn init

Adding TypeScript

# NPM
npm install -D typescript @types/node nodemon
# Yarn
yarn add -D typescript @types/node nodemon

• Dependencies
  • typescript - Compiler For TypeScript
  • @types/node - Types For Node.js
  • nodemon - Restarts The Server On Changes

Open Your package.json And Add Scripts To It

"scripts": {
    "start": "node dist/index.js",
    "dev": "nodemon dist/index.js",
    "watch": "tsc -w"
}

Now We Need A tsconfig.json, So Instead Of Typing tsconfig.json From Scratch Let's Generate It

npx tsconfig.json

Select Node.js When Asked To Enter Your Framework

Run The Application

Create a File src/index.ts And Add This Code To It

console.log('hello world')

Now Open a Terminal And Run watch Command

# NPM
npm run watch
# Yarn
yarn watch

Open Another Terminal And Run dev Command

# NPM
npm run dev
# Yarn
yarn dev

You Should See hello world

Add TypeORM

# NPM
npm install typeorm pg reflect-metadata
# Yarn
yarn add typeorm pg reflect-metadata

• Dependencies
  • typeorm - Base TypeORM Package
  • pg - Postgres Driver For Node.js
  • reflect-metadata - Required For TypeORM

Now We Can Create A Connection To Our Database Open src/index.ts and add async connection to typeorm

import "reflect-metadata"
const main = async () => {
    console.log('hello world')
}
main().catch(err => console.error(err))

Now we can use async/await syntax inside main function we can setting up typeorm connection using the createConnection function

// src/index.ts
import "reflect-metadata"
import { createConnection } from "typeorm"
const main = async () => {
    await createConnection({
        type: "postgres", // DATABASE TYPE
        host: "localhost", // DATABASE HOST
        port: 5432, // DATABASE PORT (DEFAULT FOR POSTGRES)
        username: "test", // USERNAME
        password: "test", // PASSWORD
        database: "test", // DATABASE
        logging: true, // LOG THE GENERATED SQL
        synchronize: true // FALSE ON PRODUCTION
    })
}
main().catch(err => console.error(err))

Creating An Entity (Table)

// src/entities/User.ts
import { Entity, PrimaryGeneratedColumn, Column, BaseEntity } from "typeorm";
@Entity()
export class User extends BaseEntity {
    @PrimaryGeneratedColumn()
    id: string;
    @Column()
    firstName: string;
    @Column()
    lastName: string;
    @Column()
    isActive: boolean;
}

Now if you open your terminal running the dev command you should see generated SQL

CRUD

CREATE

const user = new User({firstName: "Nouman", lastName: "Rahman", isActive: true});
await User.save(user)

READ

await User.find() // Give All Users
await User.findOne("1") // Give The User With ID ("1")

UPDATE

await User.update({id: 1}, {firstName: "Nouman"}) // Update firstName Of The User With ID ("1")

DELETE

await User.delete({id: 1}) // Delete The User With ID ("1")