@karan’s answer already points to the solution which worked for me, but being inexperienced / not-a-professional-developer, it took me a little work to translate it into a working solution to the original question. Here’s a concise description of the steps I used to perform this task:
-
Create the following function in my script:
function deleteForever(userId, labelName) { var threads = GmailApp.search("in:trash label:" + labelName); for (var i = 0; i < threads.length; i++) { Gmail.Users.Messages.remove(userId, threads[i].getId()); } }
-
To enable advanced services for this script, locate
Resources
on the menu, and selectAdvanced Google services...
-
Enable
Gmail API
on the list. -
Before selecting
OK
, click on theGoogle Developers Console
link. Search forgmail
, and enable the service there as well. -
Done, select
OK
; the function should now work. (Comment: as mentioned in the link @karan provided, one can use"me"
for userID, or alternatively provide one’s Gmail address:"<address>@gmail.com"
.)
(Steps to enable advanced services for my script are based on Google’s guide here.)