The validation methods are passed 2 parameters: value and element.

Some methods use element.value when validating, instead of the 'value' parameter which prevents nesting those methods in others.

eg. if I wanted to let the user type multiple e-mail addresses separated by a comma I would create a validation method which splits the text apart and then passes each piece to the 'email' validation method.

Validation methods probably weren't meant to be nested but it would be nice to be able to use them whenever possible.