33 - Form Validation with Error Messages

Description

Create a React component that validates user input in a form and displays appropriate error messages.

• Handles various form input types (text, email, password, etc.).

• Defines validation rules for each field (required, email format, password strength, etc.).

• Displays error messages near invalid fields, indicating the validation issue.

• Prevents form submission until all fields are valid.

Algorithm

1. Component Structure:

   • Define a functional component named FormValidator.

   • Accept props for:

     • formData: Object containing initial form field values.

     • validationRules: Object defining validation rules for each field.

     • onSubmit: Function to handle form submission when valid.

   • Maintain internal state for:

     • formErrors: Object tracking errors for each field.

     • isSubmitting: Boolean flag indicating form submission in progress.

2. Initial Validation:

   • Use a useEffect hook to run initial validation on formData and update formErrors state.

3. Form Rendering:

   • Render form elements (input fields, labels, etc.).

   • Display error messages below or next to corresponding fields using conditional rendering.

   • Disable the submit button if there are errors or submission is in progress.

4. Input Handling:

   • Attach event listeners to input fields to track changes.

   • Update formData state with new values.

   • Run validation logic for the changed field and update formErrors accordingly.

5. Form Submission:

   • Attach an event listener to the submit button.

   • Prevent default form submission behavior.

   • Check for errors and prevent submission if any exist.

   • If valid, set isSubmitting to true, call the onSubmit prop with formData, and reset errors after completion.

Code

// Some code