Need help with Scriptrunner Script to check for either of one field ?

[Aisha M]

I have two field,

Field 1 - ParentName

Field 2- Child Link 

I want to modify the existing script to say,

If Field 1 is empty, check for Field 2,

OR, Only if Field 1 is filled , skip the check for Field 2.

How to I write a Scriptrunner script for this scenario. Please help.

[Subrat Mishra]

What's is the exact requirement ? You need it as a behaviour or listener/post-function ?