Imagine spending your time filling out a long form, submitting it, and then receiving an error message. It is incredibly frustrating. This is where inline validation comes in. Inline validation checks user inputs for errors and informs them immediately.


How do you implement inline validation properly?


Side note

Credit card numbers can be validated using the Luhn algorithm, which finds out whether the card number sequence has been correctly typed. It does not validate whether the number is valid or whether the card has sufficient funds.