Using TypeORM in JavaScript: A Comprehensive Guide with Example Usage of Datasource, Endpoint, Repository, and Entity

Discover how to use TypeORM in JavaScript with this comprehensive guide. Learn the process of configuring a datasource, creating an endpoint, setting up a repository, and defining entities. Includes a detailed example for seamless integration into your projects. Start leveraging the power of TypeORM for efficient database interactions.

TypeORM is a powerful Object-Relational Mapping (ORM) library that allows you to interact with databases using JavaScript or TypeScript. It supports a wide range of databases, including PostgreSQL, MySQL, SQLite, and others. In this essay, we will explore the basics of using TypeORM and demonstrate its usage through an example.

To get started with TypeORM, you need to set up a JavaScript project. Create a new directory for your project and navigate to it in your terminal. Initialize a new npm project by running the following command:

npm init -y

Once the project is initialized, you can install TypeORM and the database driver of your choice. For example, if you want to use PostgreSQL, you can install the pg package:

npm install typeorm pg

Now, let’s move on to the example usage of TypeORM. We will demonstrate how to set up a datasource, define an entity, create a repository, and perform basic CRUD operations.

  1. Datasource: A datasource in TypeORM represents a connection to a database. To configure a datasource, create a ormconfig.json file in the root of your project directory with the following content:
  "type": "postgres",
  "host": "localhost",
  "port": 5432,
  "username": "your_username",
  "password": "your_password",
  "database": "your_database",
  "synchronize": true,
  "logging": true,
  "entities": ["src/entities/*.js"],
  "migrations": ["src/migrations/*.js"],
  "subscribers": ["src/subscribers/*.js"]

Make sure to replace the placeholder values with your actual database credentials.

  1. Entity: An entity in TypeORM represents a table in the database. Create a new directory called entities in your project’s src folder. Inside this directory, create a new JavaScript file, for example User.js, and define your entity class as follows:
class User {
  constructor(name, email) { = name; = email;

You can also use decorators provided by TypeORM to define your entity with more details such as column types, relationships, and validations.

  1. Repository: A repository in TypeORM provides methods for performing database operations related to a specific entity. Create a new directory called repositories in your project’s src folder. Inside this directory, create a new JavaScript file, for example UserRepository.js, and define your repository class as follows:
import { EntityRepository, Repository } from 'typeorm';

class UserRepository extends Repository {
  // Custom methods and queries can be defined here
  1. Endpoint: Now, let’s create an example endpoint using a web framework like Express.js. Install the express package:
npm install express

Create a new JavaScript file, for example app.js, and define your endpoint as follows:

import express from 'express';
import { createConnection } from 'typeorm';
import UserRepository from './repositories/UserRepository';

const app = express();

app.get('/users', async (req, res) => {
  const connection = await createConnection();
  const userRepository = connection.getCustomRepository(UserRepository);
  const users = await userRepository.find();

app.listen(3000, () => {
  console.log('Server is running on port 3000');

This endpoint sets up a simple HTTP server using Express.js on port 3000. When a GET request is made to the /users endpoint, it establishes a connection to the database using createConnection(), retrieves the UserRepository using getCustomRepository(), and fetches all users from the database using the find() method of the repository. Finally, it responds with a JSON representation of the users. To run the example, you can add a new script in your package.json file:

  "scripts": {
    "start": "node app.js"

Now, you can start the server by running the following command:

npm start

Visiting http://localhost:3000/users in your browser or using an API testing tool like Postman will fetch the list of users from the database and display them in JSON format.

This example demonstrates the basic usage of TypeORM in JavaScript. You can further explore TypeORM’s documentation to learn about advanced features like migrations, relationships, and more complex query operations.

TypeORM simplifies database interactions by providing a robust and flexible ORM solution for JavaScript. With its intuitive API and support for various databases, it allows developers to focus on building applications without worrying about low-level database operations.

In conclusion, by following the steps outlined above and using the example usage of a datasource, endpoint, repository, and entity, you can begin leveraging the power of TypeORM in your JavaScript projects to manage your database interactions efficiently.