Q27: How do you validate incoming request payloads in Express?
Request payload and parameter validation is handled using validation middleware like express-validator or zod.
Validating Inputs using express-validator
const { body, validationResult } = require('express-validator');
app.post('/user',
body('email').isEmail().normalizeEmail(),
body('password').isLength({ min: 8 }),
(req, res) => {
const errors = validationResult(req);
if (!errors.isEmpty()) {
return res.status(400).json({ errors: errors.array() });
}
res.json({ success: true });
}
);💡 Validation middleware sanitizes and inspects incoming request fields before proceeding.
Key Takeaways
- Validate payload body fields, params, and query strings before touching database layers.
- Reject invalid requests early with 400 Bad Request responses.