Are there any form input components that do javascript driven validation

Hi all,

So if I want to display a text input in a form I use 
textInputWithCallback.  Is there an API that allows me state 
validation rules that must be performed on that text input and 
have those rules enforced on the browser using javascript?  If 
not, could somebody please offer a few lines of guidance on how 
best to do this the seaside way?
Thanks very much,
Mike