The Git tag for this section is chapter-5-exercises.
- Add a feature to clear any validation errors when the user corrects them. Use the onChange handler for this rather than onBlur, since we want to let the user know as soon as they've corrected the error.
- Add a feature that disables the Submit button once the form has been submitted.
- Write tests for each of the functions within the formValidation module.
- The handleSubmit function is long. Extract a doSave function that pulls out the main body of the if statement.
