function gmailAutoarchive() {
  var archived_threads = 0;
  var delayDays = 2;
  
  var maxDate = new Date();
  maxDate.setDate(maxDate.getDate()-delayDays); // what was the date at that time?
  
  // getUserLabels returns an array of gmail labels. 
  // This way we don't have to convert the array elements and will archive all user labeled threads.
  var labels = GmailApp.getUserLabels() 
  var threads = GmailApp.getInboxThreads(0, 400);

  // we archive all the threads if they're unread AND older than the limit we set in delayDays
  for (var i = 0; i < threads.length; i++) {
    var thread = threads[i];      

    if (thread.getLastMessageDate()<maxDate){      
      var thread_labels = thread.getLabels();  
      
      for (var j = 0; j < thread_labels.length; j++){
         
         if (labels.includes(thread_labels[j])){
            thread.moveToArchive();
            archived_threads += 1;
            break;
          }
      }
    }
  }
  console.log("archived "+archived_threads+" threads")
}