how to create ScriptRunner Listener that updates story points based on two number fields ?

[Jacob Francois]

Has anyone ever created a code that add two number fields custom fields ?

QE story point + Dev Story point = Jira Story points 

I would use a scripted field but we want to continue using Jira's Story point field. 

I would like this to happen when an issue update event happens only for one project category. 

[Craig Nodwell]

There's lots in the Scriptrunner Library that should help you get a solid start.
This shouldn't be too difficult to achieve, here's an example of updating a custom filed based on a calculation.  The Story Points field update shouldn't be very different.

Adaptavist Library Calculate Custom Field On Issue Update 

The Adaptavist Library 

Hope this helps.