Creating a TypeScript Fastify API Project

Fastify is a fast and low-overhead web framework for Node.js. It is highly performant and provides a rich plugin ecosystem. When combined with TypeScript, it allows you to build robust and type-safe APIs. In this blog post, we’ll walk through the steps to set up a Fastify API project with TypeScript.

Prerequisites

Before you begin, ensure you have the following installed on your machine:

• Node.js (v14 or later)
• npm (v6 or later)

Step 1: Set Up the Project

First, create a new directory for your project and initialize a new Node.js project:

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

This will create a package.json file in your project directory.

Step 2: Install Dependencies

Next, install Fastify and TypeScript along with their respective type definitions:

npm install fastify
npm install -D typescript @types/node ts-node

Step 3: Configure TypeScript

Create a tsconfig.json file in the root of your project with the following content:

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

Step 4: Set Up the Project Structure

Create a src directory and add an index.ts file inside it:

mkdir src
touch src/index.ts

Step 5: Write the Fastify Server Code

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

import fastify from 'fastify';

const server = fastify({ logger: true });

server.get('/', async (request, reply) => {
  return { message: 'Hello, Fastify with TypeScript!' };
});

const start = async () => {
  try {
    await server.listen(3000, '0.0.0.0');
    server.log.info(`Server listening on http://localhost:3000`);
  } catch (err) {
    server.log.error(err);
    process.exit(1);
  }
};

start();

This code sets up a simple Fastify server with a single route (/) that returns a JSON response.

Step 6: Add Scripts to package.json

Update the scripts section of your package.json to include the following scripts:

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

• build: Compiles the TypeScript code to JavaScript.
• start: Runs the compiled JavaScript code.
• dev: Runs the TypeScript code directly using ts-node for development.

Step 7: Run the Server

To start the development server, run:

npm run dev

You should see output indicating that the server is running. Open your browser and navigate to http://localhost:3000. You should see the message {"message":"Hello, Fastify with TypeScript!"}.