Auto Populate the fields in Jira Cloud

[mounika.p]

Is there any option to auto populate the fields during creation of ticket. I have two custom fields A and B. Depending On custom Field A the custom field B should auto populate its value which i would like to set. 

I am a beginner in JIRA Cloud. So can anyone give me a step-by-step procedure to achieve this.

[Jon Bevan _Adaptavist_]

This isn't possible with the functionality that JIRA Cloud provides as standard, but you can use an add-on like ScriptRunner for JIRA Cloud to set the custom field in a post function on your workflow. The documentation here might help you.