Acrobat Form Field RegEx Validation

Question

I have a form field in my PDF that requires five capitalized letters as input, or nothing at all. Everything else should result in an error. I got the first part working, but I'm making some kind of mistake in checking for an empty field. Here's my Javascript:

 event.rc = true; var myRegExp = /^[AZ]{5}$/; var myTextInput = event.value; if ( !myRegExp.test(myTextInput) || myTextInput != "" ) { app.alert("Your order number prefix must be formatted as five characters, all caps."); event.rc = false; } 

Answer 1

Change the regex to

var myRegExp = /^([A-Z]{5})?$/;

to allow an empty string match and remove || myTextInput != "" || myTextInput != "" condition that becomes irrelevant.

A (...)? group is an optional one because ? matches 1 or 0 occurrences of the quantified subpattern.