How to validate in React JS?

@lily 

In React JS, you can validate user inputs using various techniques. Here are some common methods to perform validation in React JS:

1. Controlled Components: Use controlled components by maintaining the state of the input fields and validating the value on each change event. You can define validation logic using conditional statements or regular expressions and update the state accordingly. Display error messages based on the validation results.
2. Form Validation Libraries: Utilize third-party form validation libraries such as Formik, Yup, or React Hook Form. These libraries provide pre-built form validation functionalities and easy integration with React JS. You can define validation schemas, error messages, and validation rules to handle form input validations.
3. Custom Validation: Write your own custom validation functions that check the input values against specific rules. You can create separate validation functions for different input types, and call them when needed. Display error messages based on the returned validation results.
4. Inline Validation: Validate the inputs in real-time by displaying immediate feedback to the users. For example, you can use onBlur or onChange events to validate each input field as the user types or moves focus away from the field. Show error messages or visual indicators based on the validation results.
5. Server-side Validation: Besides client-side validation, it is crucial to perform server-side validation to ensure data integrity and security. Send the submitted form data to the server and validate it against the predefined validation rules on the server-side. Return error messages or status codes if the validation fails.

Remember to apply validation on key fields, such as required fields, email addresses, numbers, or lengths, based on your specific use case. Handle displaying error messages or styles to indicate validation failures to the users to provide a better user experience.