Foul

Foul is a JavaScript based, form validation language. If you hate all the rigamarole you have to go through just to check a simple web form, then this script is what you need. Foul contains a full language parsing engine which compiles advanced conditions and tests for the fields of a form. The language makes building tests as easy as saying what you want. The tests include, blank fields, numbers, phone numbers, credit cards, urls, zip codes, states, emails, social security numbers, ranges, lengths, dates, file types and much more. Foul also contains an auto-formatting feature which fixes the data before it's sent.