The regular expression pattern checking is pretty awesome. I'll disagree though where they say you don't need any more server side validations. You can easily remove / change the pattern value in the DOM. Which begs the question, what's the integrity of client-side testing if it cam be bypassed so easily?
anything client-side is never about security or consistency since no matter what you do, anybody can always send you any data they want.
client side validity checking is about the user experience, I mean if the user is doing something wrong you can guide them to the right direction without the need of server interaction and server interaction is always slower that one line of client side code.
