# Parsing & Sending JSON — Express.js

Source: https://www.geekswithgeeks.com/en/expressjs/ex-json-bodies

> express.json() in, res.json() out.

## Parsing an incoming body

Without `express.json()`, `req.body` is `undefined`. With it, a JSON payload becomes a plain object.

```javascript
app.use(express.json());

app.post('/items', (req, res) => {
  const { name, price } = req.body;
  res.status(201).json({ name, price, id: Date.now() });
});
```

## Sending JSON back

`res.json(obj)` stringifies `obj` and sets `Content-Type: application/json` automatically.

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

## Content-Type must match

`express.json()` only parses requests sent with `Content-Type: application/json` — otherwise `req.body` stays empty.