Custom validation in google forms using Google script on focus out the field

Question

Is this possible to check to validate a text field on focus out in google forms? Need to check for the unique value and notify the user about an error.

Answer 1

Google forms allow only onload and onsubmit events, so seems no way to check on change, on blur or something like that. "Built-in" capability is quite good, but doesn't cover this situation.