Question - How to use custom validate in a registation field

Dear friends of chronoforms forum.
Since many many days ago i am wondering how i can validate the content on a field of a custom registration form.
The code is javascript code to be run on the client side.
i dont know if i am clear, you can validate a field by "requiered", "number", "alpha", etc, what i want is to validate one field by "my custom js code".
is this posible??
regards.
Gonzalo.

Hi Gonxalo,

Please see this FAQ

Bob

Dear Bob,
thank you for the link, i dont understand this part:
Then add this into the Class box of the element that you want to validate:

How i do that??

Hi gonzagnr,

In the form Editor go to the Preview tab, open the element that you want to validate and scroll down to find the Field class box.

Bob