How can I implement input validation in Express.js?

How can I implement input validation in Express.js?

You can use middleware like 'express-validator' to validate user input in your Express.js application.

Can you show me a simple example of using express-validator?

Sure! First, install it using npm: npm install express-validator. Then, you can use it like this:

const { body, validationResult } = require('express-validator');

app.post('/user', [
  body('email').isEmail(),
  body('password').isLength({ min: 5 })
], (req, res) => {
  const errors = validationResult(req);
  if (!errors.isEmpty()) {
    return res.status(400).json({ errors: errors.array() });
  }
  // Proceed with user creation
});

What happens if the validation fails?

If validation fails, the validationResult will contain the errors, and you can send a response with the error details, as shown in the example.