What are the best practices for handling invalid data in web forms?

Data validation involves checking input data to ensure it meets specified criteria and formats. This process helps maintain data accuracy, security, and usability by preventing invalid or malicious data submissions. It enhances user experience and reduces the risk of security vulnerabilities.

Client side validation is first line of defense for protecting your apps from invalid data you can use different tools and libraries provided by JavaScript community to provide validation mechanisms for your application some of must popular choices are formik or react hook form library for react developers. But it's essential to notice that clients sudden validation can bypass by population malicious has client side js scipts. It's also essential to provide suitable feedbacks for your users to encourage them to provide correct data formats.

Client-side validation is a method of validating user input in web forms using JavaScript. It provides immediate feedback to users, enhancing the user experience by catching errors as data is entered. However, it should be complemented with server-side validation for security and data integrity.

- While client side validation provides some kinda shield to backend, but there is always a possibility that client may not have implemented the validation correctly. As backend developers our APIs will be used by several clients, so just relying on client side validation is not viable. - On node.js using express, validation could be carried out using middlewares, but with latest frameworks like nestjs, which provides support like class-validator which helps in providing validation in more expressive ways.

Server-side validation is a defecto standard for protecting your databases from a storing invalid data a storing invalidator inside your databases and backend system can also lead to very complex and hard to find bugs and in some cases can a hacker can access your sensitive data or maybe run malicious SQL descripts using SQL injection techniques. All popular web frameworsk like Django, laravel and spring boot and .net provide comprehensive validation logics for protecting you from the storing invaded data inside your systems. You should never trust your users for providing correct data and always you should validate data before any processing.

Server-side validation is the process of validating user input and data on the web server after it's submitted, ensuring accuracy, security, and compliance with validation rules. It provides a crucial layer of defense against security threats like SQL injection and guarantees data integrity. Combining it with client-side validation creates a robust and secure web application.

Data validation best practices include implementing both client and server-side validation, using whitelisting instead of blacklisting, and sanitizing input data to prevent security vulnerabilities. Employing well-tested libraries, custom validation rules, and comprehensive error handling is crucial. Regular updates, security testing, and user education enhance data validation practices, promoting robust security and data integrity.

One of the other techniques that you can protect your applications from malicious users and hackers that you can define logics to block IP addresses that sent invalid data to your application repeatedly. Always try to follow this security practices to defend privacy and security of your system