Form fill - overwrite fields when the values are blank

with some mktoForm js you could change the field values to be "NULL" on submit if the field value is empty

To achieve this:

you can set default values.

or 

you can use JS

The problem with simply setting the value to NULL using JS (and it's even more obvious if you set a default value) is the user sees the word NULL, which looks unprofessional IMO.

I have a blog post coming out next week where I show how to set the value to NULL while the field still looks empty to the end user (and no, it doesn't use a hidden field!).

In other words, instead of this confusing experience:

This smoother one: