What are client-side and server-side validations in Web pages?

In web development, client-side and server-side validations are two different approaches to validating user input in web forms.

1. Client-side validation:
   • Client-side validation is performed on the user’s device (usually in a web browser) using JavaScript or other client-side scripting languages.
   • It provides immediate feedback to the user without needing to communicate with the server, thus improving the user experience by reducing the need for round trips to the server.
   • Commonly used client-side validation techniques include checking for required fields, validating email addresses, enforcing minimum and maximum lengths, and ensuring that certain fields contain only numeric or alphabetic characters.
   • While client-side validation enhances user experience, it should be supplemented with server-side validation for security and reliability reasons.
2. Server-side validation:
   • Server-side validation is performed on the server after the form data is submitted by the user.
   • It is essential for ensuring the integrity and security of the data, as client-side validation can be bypassed or manipulated by malicious users.
   • Server-side validation typically involves checking the submitted data against business rules, database constraints, and other server-side logic.
   • Even if client-side validation is implemented, server-side validation should always be performed as a fallback to catch any issues that may have been missed or intentionally bypassed on the client side.

In an interview, it’s crucial to emphasize that while client-side validation can improve user experience, server-side validation is indispensable for data integrity, security, and adherence to business rules. Both types of validation should ideally be used in conjunction to provide the best user experience while maintaining the security and integrity of the application’s data.