React Js form validation Example

How can I perform form validation in React.js?

The provided code demonstrates an example of form validation in a React.js application. The form contains several input fields such as first name, last name, username, email, password, confirm password, and an image upload field. The validation is performed when the form is submitted by calling the handleSubmit function.

The useState hook is used to manage the form data and the validation errors. The formData state object holds the values of the form inputs, while the errors state object stores the validation error messages for each input field.

The validateForm function is responsible for validating the form inputs. It checks if the required fields are filled, validates the email format, ensures the password and confirm password match, and checks the size of the uploaded image. If any validation fails, the corresponding error message is set in the errors state object.

The handleChange function updates the formData state object as the user types or selects a file, and it also clears the corresponding error message from the errors state object.

The input fields are rendered within the form element, and their values and error messages are bound to the state objects. The CSS classes form-input and form-input-error are conditionally applied to style the input fields based on the presence of errors.

When the form is submitted and passes validation, the form data is logged to the console.