How can custom errors be utilized to improve the clarity and robustness of input validation logic in JavaScript?

Custom errors significantly improve input validation by making invalid states explicit and forcing their handling. Instead of returning `false` or `null` for invalid input, you can throw a specific custom error, like a `ValidationError`. This approach ensures that the calling code explicitly catches and addresses the validation failure, centralizes error handling, and allows the custom error object to carry rich details about the validation failure (e.g., which field was invalid, the reason), leading to more robust, readable, and maintainable code.