Hide custom fields based on drop down selection

[Garden16_]

I have a custom field that  displays User story   and Epic  (Issue type 1 and Issue type 2)

This custom field is multi issue search picker. I have created this field using the scripted field in Script runner.

I have custom Field A, Field B and Field C which have to be displayed based on the issue type selected in the drop down custom field  - User story and Epic(Issue type 1 and Issue type 2) 

If issue type 1 (user story) is selected from the drop down then the other custom fields A,B , C have to be displayed . If I select Issue type 2 (epic) the custom fields A,B , C should not be displayed .

How do I achieve it using script runner behavior code