• Validate.js (you may import its functionality into your React projects): https://validatejs.org/
• Get more ideas about potential validation approaches: https://react.rocks/tag/Validation

Alternatives to the manual approach taken in this course:

• react-validation package: https://www.npmjs.com/package/react-validation
• formsy-react package: https://github.com/christianalfoni/formsy-react