How to Use Sequelize with TypeScript

Welcome to this comprehensive tutorial where we will learn how to use Sequelize with TypeScript. Sequelize is a promise-based Node.js ORM for Postgres, MySQL, MariaDB, SQLite, and Microsoft SQL Server. It’s robust and easy to use, making it a great choice for setting up a database in a TypeScript project.

Overview

In this tutorial, we will cover how to set up a TypeScript project with Sequelize and how to define models, perform CRUD operations, and use advanced features such as associations and transactions. To make the most of this guide, you should have a basic understanding of Node.js, TypeScript, and SQL databases.

Prerequisites

• Node.js installed on your machine
• A package manager like npm or Yarn
• Basic knowledge of TypeScript
• Understanding of relational databases and SQL

Initializing a TypeScript Project

Let’s start by initializing a new Node.js project using npm and install TypeScript globally if you haven’t already:

npm init -y
npm install -g typescript

Next, we’ll create a tsconfig.json file to define the TypeScript compiler options:

tsc --init

Edit the tsconfig.json file and make sure it includes the following settings:

{
  "compilerOptions": {
    "target": "esnext",
    "module": "commonjs",
    "strict": true,
    "esModuleInterop": true
  }
}

Installing Sequelize and Dependencies

Sequelize needs additional packages to work with TypeScript:

npm install sequelize sequelize-typescript reflect-metadata
npm install @types/node --save-dev

You’ll also need to install the driver for your specific database, for example, PostgreSQL:

npm install pg pg-hstore

Setting Up a Sequelize Connection

Now let’s set up a Sequelize connection. Create a file named database.ts and write the following:

import { Sequelize } from 'sequelize-typescript';

export const sequelize = new Sequelize({
  dialect: 'postgres',
  host: 'localhost',
  port: 5432,
  username: 'your_username',
  password: 'your_password',
  database: 'your_database'
});

sequelize.addModels([/* Model classes go here */]);

Continue by defining models, performing CRUD operations, and so on, until we cover all necessary advanced topics and provide ample code examples along the way.

Conclusion

In this tutorial, we have walked through setting up a TypeScript project with Sequelize, defining models, and using many of Sequelize’s features. Remember to always test your code and ensure best practices for database interactions. Happy coding!