What are validation libraries generally used for?

Validation libraries are used to automate the verification of data correctness entered by users or received from external sources. They help ensure that data complies with specified rules (such as email format, string length, required fields) before processing or sending it to the server. This increases application reliability, improves user experience, and reduces the likelihood of errors and vulnerabilities associated with incorrect data.

Example of using a validation library in JavaScript:

import * as yup from 'yup';

const schema = yup.object().shape({
  email: yup.string().email().required(),
  password: yup.string().min(8).required(),
});

schema.validate({ email: 'user@example.com', password: '12345678' })
  .then(() => console.log('Validation passed'))
  .catch(err => console.log('Validation error:', err.errors));