Building a Web API with TypeScript

Building a Web API with TypeScript


TypeScript has emerged as a game-changer, particularly for developers coming from a strongly-typed language background like C# or Java.

It brings the power of types to JavaScript, enhancing code quality and maintainability.

If you’re looking to build a Web API using TypeScript, you’re in for a treat. This guide will walk you through the process step by step, from setting up your environment to deploying your first endpoint.

Why TypeScript for Web API Development?

Before diving into the how, let’s quickly glance at the why:

  1. Type Safety: TypeScript’s static typing helps catch errors early in the development process, reducing runtime surprises.
  2. Improved Readability and Maintainability: With types, your code is more descriptive and easier to understand.
  3. Rich Ecosystem: TypeScript is well integrated into the Node.js ecosystem, making it compatible with a wide range of libraries and tools.
  4. JavaScript Superset: You get all the JavaScript features, plus the added advantages of TypeScript.

Setting Up the Environment


  • Node.js and npm installed on your machine.
  • A text editor or IDE that supports TypeScript (like Visual Studio Code).

Step 1: Initialize a New Node.js Project

Create a new directory for your project and initialize it with npm.

mkdir my-typescript-api 
cd my-typescript-api 
npm init -y

Step 2: Install TypeScript

Install TypeScript as a development dependency.

npm install --save-dev typescript

Step 3: Configure TypeScript

Create a tsconfig.json file in your project root. This file specifies the compiler options required for your project.

  "compilerOptions": {
    "target": "es6",
    "module": "commonjs",
    "outDir": "./dist",
    "strict": true,
    "esModuleInterop": true
  "include": ["src/**/*"]

Step 4: Install Express and Types

Express is a minimal and flexible Node.js web application framework. Install Express along with its TypeScript type definitions.

npm install express 
npm install --save-dev @types/express

Building Your First API

Step 1: Create Your First Endpoint

Create a new folder named src and add a file index.ts.

Add the following code to create a simple Express server:

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

const app = express();
const port = 3000;

app.get('/', (req: Request, res: Response) => {
  res.send('Hello, TypeScript with Express!');

app.listen(port, () => {
  console.log(`Server is running at http://localhost:${port}`);

This code sets up an Express server that listens on port 3000 and responds to GET requests to the root URL (/) with a welcome message.

Step 2: Compile and Run Your TypeScript Code

Add a script to your package.json to compile TypeScript:

"scripts": { "start""tsc && node ./dist/index.js" }

Run your server using npm:

npm start

Navigate to http://localhost:3000 in your browser or use a tool like Postman to see your API in action.

Expanding Your API

Now that you have a basic API running, you can start adding more endpoints, integrate a database, and add authentication. TypeScript and Express make it easy to structure your API well. You can create separate modules for routes, controllers, services, and data models.

Deploying Your API

Once your API is ready, you can deploy it to a cloud provider like AWS, Azure, or Heroku. Ensure you set the environment variables correctly for your production environment.


Building a Web API with TypeScript and Express is not only straightforward but also results in cleaner, more maintainable code.

TypeScript’s static typing brings a level of robustness to your Node.js projects, making them easier to scale and collaborate on.

As you delve deeper, you’ll find TypeScript’s ecosystem rich and supportive, opening doors to advanced features like decorators, generics, and much more.

So, embrace TypeScript and elevate your web API development to the next level!

The official TypeScript documentation can be found here: –

I have a few related posts here: – TypeScript for C# Developers – making a move, Understanding TypeScript Promises


Hi, my name is Stephen Finchett. I have been a software engineer for over 30 years and worked on complex, business critical, multi-user systems for all of my career. For the last 15 years, I have been concentrating on web based solutions using the Microsoft Stack including ASP.Net, C#, TypeScript, SQL Server and running everything at scale within Kubernetes.