How can I validate user input in Express using middleware?

How can I validate user input in Express using middleware?

You can use middleware functions in Express to validate user input. Libraries like Joi or express-validator are popular choices.

Can you show me an example using express-validator?

Sure! First, install express-validator. Then, you can create a middleware function 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 middleware will return a 400 status code along with the validation errors in the response.