This guide will walk you through setting up an Express.js server using TypeScript. The setup includes TypeScript configuration, development dependencies, and scripts for building and running the server.

Make sure you have Node.js installed.

Create a new project folder, navigate into it, and initialize it with npm init.

mkdir my-express-ts-server
cd my-express-ts-server
npm init -y

Install Express, TypeScript, and types for Node.js and Express. We’ll also install ts-node and nodemon for easier development with TypeScript.

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

Initialize TypeScript configuration with:

npx tsc --init

This will create a tsconfig.json file. Here are some suggested modifications to enable better compatibility for Node.js and Express:

{
  "compilerOptions": {
    "target": "ES6",
    "module": "commonjs",
    "rootDir": "./src",
    "outDir": "./dist",
    "strict": true,
    "esModuleInterop": true,
    "skipLibCheck": true
  },
  "include": ["src/**/*.ts"],
  "exclude": ["node_modules"]
}

• rootDir: Specifies the root directory of our source files.
• outDir: Specifies the output directory for compiled files.

Create the following project structure:

my-express-ts-server/
├── src/
│   └── index.ts
├── tsconfig.json
├── package.json
└── README.md

In src/index.ts, set up a basic Express server:

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

const app = express();
const PORT = process.env.PORT || 5000;

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

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

Add the following scripts to simplify building and running the server:

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

• build: Compiles the TypeScript code into JavaScript in the dist folder.
• start: Runs the build script, then starts the compiled server with Node.js.
• dev: Uses nodemon and ts-node to run the server in development mode with auto-reloading.

For development with live reloading:

npm run dev

For production (after compiling TypeScript files):

npm start

Once the server is running, open a browser or use a tool like curl or Postman to visit http://localhost:3000. You should see the message:

Hello, TypeScript with Express!