Why should you care?

Every MernVerse feature needs a stable HTTP entrypoint before React can call it.

See it live — copy this example

Run examples in your MernVerse client/ (Vite React) or server/ (Express) folders. Keep secrets in .env.

import express from 'express';
import cors from 'cors';

const app = express();
app.use(cors({ origin: 'http://localhost:5173' }));
app.use(express.json());

app.get('/api/health', (_req, res) => res.json({ ok: true }));

app.listen(5000, () => console.log('API on :5000'));

Run Example »

Edit the code below and click Run to see the result in Toolliyo’s live editor.

What happened?

• cors allows the Vite origin in dev.
• express.json parses bodies.
• Health checks prove the process is up.

Practice next

1. npm init and install express cors.
2. Add "type": "module" or use require.
3. Hit /api/health in the browser.
4. Add a notes router stub.
5. Move listen into server.js and app into app.js.

Remember

JSON middleware first. Mount /api routers. Health endpoint helps deploy.

API boots

React needs a backend today.

Outcome: Health returns { ok: true }.