This recipe uses the jQuery JavaScript library, which is bundled with Jira. If you are not familiar with jQuery, you can find the documentation at http://jquery.com.

We will also need to use the custom field's ID in our script, so you will need to have that handy. You can find the ID by going to the Custom fields page, clicking on the Edit link of the target field, and clicking the number at the end of the URL, which is the field's ID. For example, the following URL shows a custom field with the ID 10103:

http://jira.localhost.com:8080/secure/admin/EditCustomField!default.jspa?id=10103