Node.js API Starter (Express)

Before you start

node --version    # want 20+

Scaffold

mkdir my-api && cd my-api
npm init -y
npm install express

Open package.json and add two things — ES modules and scripts:

{
  "type": "module",
  "scripts": {
    "dev": "node --watch --env-file=.env server.js",
    "start": "node server.js"
  }
}

Modern Node has hot reload (--watch) and .env loading built in — no nodemon, no dotenv package.

The server

Create server.js:

import express from 'express';

const app = express();
app.use(express.json());

app.get('/health', (req, res) => {
  res.json({ status: 'ok' });
});

app.post('/echo', (req, res) => {
  res.json({ youSent: req.body });
});

const port = process.env.PORT ?? 3000;
app.listen(port, () => console.log(`API listening on http://localhost:${port}`));

Create .env (and add it to .gitignore):

PORT=3000

Run it

npm run dev

Test from another terminal:

curl http://localhost:3000/health
curl -X POST http://localhost:3000/echo -H "Content-Type: application/json" -d "{\"hello\":\"world\"}"

Growing past one file

my-api/
├── server.js         # app setup + listen
├── routes/           # one file per resource: users.js, orders.js
├── middleware/       # auth, logging, error handler
└── .env

Wire a route file in with app.use('/users', usersRouter).

Common gotchas

• require is not defined: you're in ES-module mode ("type": "module") — use import, not require.
• Cannot use import statement outside a module: the opposite — you forgot "type": "module" in package.json.
• POST body is undefined: missing app.use(express.json()), or the request lacks the Content-Type: application/json header.
• Port already in use: change PORT in .env — that's why it's there.