How do I implement server-side validation in my web application?

How do I implement server-side validation in my web application?

To implement server-side validation, you need to check the data on the server after it has been submitted by the user. This typically involves using a programming language like PHP, Node.js, or Python to validate the input against certain rules.

What are some common validation rules I should consider?

Common validation rules include checking for required fields, validating email formats, ensuring passwords meet complexity requirements, and checking for unique values in the database.

Can you give me an example in Node.js?

Sure! In Node.js, you can use libraries like Joi or express-validator. For example, using Joi, you can define a schema and validate the request body like this:

const Joi = require('joi');

const schema = Joi.object({
  username: Joi.string().min(3).required(),
  email: Joi.string().email().required(),
  password: Joi.string().min(6).required()
});

const { error } = schema.validate(req.body);
if (error) {
  return res.status(400).send(error.details[0].message);
}

What should I do if validation fails?

If validation fails, you should return an appropriate error message to the user, indicating what went wrong, and possibly highlight the fields that need correction.