Some rule nodes have specific UI feature that allow users to test JS functions. Once you click on the Test Filter Function you will see the JS Editor that allows you to substitute input parameters and verify the output of the function.
You can define:
- Message Type in the top left field.
- Message payload in the left Message section.
- Metadata in right Metadata section.
- Actual JS script in Filter section.
After pressing Test output will be returned in right Output section.