New to Jira - Events?

[CJ_Marchand]

Hello everyone.

New to Jira/Jira Admin but have an extensive background in coding.

I have a user that would like to have a text box populated when someone picks a value from a picker field when creating an issue.

First up I am used to event driven web sites where each control has events you can code against.  I am not seeing this in Jira.  

Can anyone point me to docs/tutorials on how to get access to events?  I created some code and placed it in a custom script field but do not know how to link this code to an evert to fire it off.  

Thanks,

cj