Express: your first web server

import express from 'express';

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

const trains = [
  { id: 12951, name: 'Mumbai Rajdhani', from: 'Mumbai' },
  { id: 12627, name: 'Karnataka Express', from: 'Bengaluru' },
];

app.get('/api/trains', (req, res) => {
  res.json(trains);
});

app.post('/api/trains', (req, res) => {
  const train = req.body;
  trains.push(train);
  res.status(201).json(train);
});

app.listen(3000, () => {
  console.log('API running on http://localhost:3000');
});

// GET /api/trains/12951
app.get('/api/trains/:id', (req, res) => {
  const id = Number(req.params.id);
  const train = trains.find((t) => t.id === id);
  if (!train) return res.status(404).json({ error: 'Train not found' });
  res.json(train);
});

// GET /api/search?from=Mumbai
app.get('/api/search', (req, res) => {
  const from = req.query.from;
  res.json(trains.filter((t) => t.from === from));
});

my-api/
  package.json
  .env
  src/
    server.js          starts the app (app.listen)
    routes/
      trains.js        which URL goes to which controller
    controllers/
      trains.js        reads req, sends res
    services/
      trains.js        the real rules (search, fares)
    db/
      index.js         talks to the database

npm run dev     # restarts the server when you save a file
npm start       # runs it normally, like on the real server