How to Write a REST API in TypeScript in 30 Minutes

Introduction: Why TypeScript for REST API?

Modern web development is unthinkable without creating efficient and secure APIs. TypeScript, as a superset of JavaScript, offers static typing, which significantly reduces the number of runtime errors and improves code readability. In this guide, we will show you how to write a full-fledged REST API in TypeScript in just 30 minutes. You will learn how to set up a project, create basic endpoints, and handle errors. This tutorial is perfect for beginner developers who want to quickly master building server-side applications.

Environment Setup and Dependency Installation

First, you need to create a new project and install all the necessary packages. Make sure you have Node.js (version 18 or higher) and npm installed.

Step 1: Project Initialization

Open a terminal and run the following commands:

mkdir my-rest-apicd my-rest-apinpm init -y

Step 2: Installing TypeScript and Dependencies

Install TypeScript, Express, and the necessary types:

npm install expressnpm install -D typescript @types/node @types/express ts-node nodemon

• express — framework for creating a server.
• typescript — TypeScript compiler.
• @types/express — types for Express.
• ts-node — for running TypeScript directly.
• nodemon — automatic server restart on changes.

Step 3: Configuring tsconfig.json

Create a tsconfig.json file in the project root:

{  "compilerOptions": {    "target": "ES2020",    "module": "commonjs",    "outDir": "./dist",    "rootDir": "./src",    "strict": true,    "esModuleInterop": true,    "skipLibCheck": true  },  "include": ["src/**/*"],  "exclude": ["node_modules"]}

Creating a Basic Server in TypeScript

Now let's create the folder structure and the main server file.

Step 4: Project Structure

Create a src folder and a src/index.ts file:

mkdir srctouch src/index.ts

Step 5: Writing the Server

Open src/index.ts and add the following code:

import express, { Request, Response } from 'express';

const app = express();const PORT = process.env.PORT || 3000;

// Middleware for parsing JSONapp.use(express.json());

// Basic routeapp.get('/', (req: Request, res: Response) => {    res.send('REST API on TypeScript is working!');});

// Start the serverapp.listen(PORT, () => {    console.log(`Server running on port ${PORT}`);});

Step 6: Adding Scripts to package.json

Update package.json by adding scripts for development and build:

"scripts": {  "dev": "nodemon --exec ts-node src/index.ts",  "build": "tsc",  "start": "node dist/index.js"}

Now start the server with the command npm run dev. You should see the message "Server running on port 3000".

Implementing CRUD Endpoints

Let's create a simple data model and implement Create, Read, Update, and Delete (CRUD) operations. For the example, we'll use the "Task" entity.

Step 7: Creating the Model and Storage

Create a file src/models/Task.ts:

export interface Task {    id: number;    title: string;    completed: boolean;}

// Temporary in-memory storageexport const tasks: Task[] = [    { id: 1, title: 'Learn TypeScript', completed: false },    { id: 2, title: 'Write REST API', completed: false },];

Step 8: Creating Routes

Create a file src/routes/tasks.ts:

import { Router, Request, Response } from