I recently ordered a new credit card. I used the price comparison websites to find the best one that met my requirements.
I notice that these websites have a lot of validation on the client side. For example please see here: https://www.moneysupermarket.com/credit-cards/search/?goal=CC_ALLCARDS&purpose=AllCards&from=SSComponent. If you enter an invalid date of birth (under 18 years old), then there is client side validation that immediately says: "Unfortunately we can only provide product information to users aged between 18 and 99 years of age.". I would expect this logic to be in the domain layer rather than the presentation layer.
The reason I ask is because I read an article recently that said the website in question are champions of DDD? Is there a pattern/approach I am missing here. Is the presentation layer calling the domain layer through AJAX?