Neat. But I don't understand why you used strings as part of the validation?

The "min_length(6)|required" isn't actual javascript code is it?

Would passing an object be better?

For example,

userForm.addValidation("username", "min_length(6)|required");

Becomes,

userForm.addValidation("username", {min_length:6, required:true});

Did I misunderstand something?