Have you ever used libraries for data validation?

Yes, I have used libraries for data validation on the frontend. For example, I often used the Yup library for form validation in React applications. It allows you to declaratively describe validation schemas and handle errors conveniently.

Example of using Yup:

import * as Yup from 'yup';

const schema = Yup.object().shape({
  email: Yup.string().email('Invalid email format').required('Required'),
  password: Yup.string().min(6, 'Minimum 6 characters').required('Required'),
});

// Data validation
schema.validate({ email: 'test@example.com', password: '123456' })
  .then(() => console.log('Validation passed'))
  .catch(err => console.log(err.errors));

Using such libraries helps to centralize and simplify validation logic, as well as improve UX through informative error messages.