Google appscript to delete mail older thant N days and having a given label

Code.gs

function deleteOldMailFromTag() {
  // push this function onto https://script.google.com/
  // to make a dry run, set sendReport to true, and removeMail to false.
  //
  // common config
  var sendReport = true;  // send script execution log by email
  var removeMail = false; // set it to true only after strong tests :)

  var tag = 'myLabel';
  var minAge = '30d';

  // internal config
  var myFilter = 'label:' + tag + ' older_than:'+minAge;
  var maxMail = 100;
  var reportRecipient = '[email protected]';
  var reportTitle = 'GGScript deleteOldMailFromTag report';

  // business process  
  Logger.log("deleteOldMailFromTag : sendReport=" + sendReport + " removeMail=" + removeMail + " filter:" + myFilter);
  
  // get back mail from my gmail (authorization required the first time)
  var threads = GmailApp.search(myFilter, 0, maxMail);
  
  // for each thread (mail group)
  for (var i=0; i < threads.length ; i++ ) {
    var t = threads[i];
    // append to the logger a line per thread
    Logger.log("DELETE >>> " + t.getFirstMessageSubject());
    // remove it if removeMail == true
    if (removeMail) {
      t.moveToTrash();
    }
  }

  // send a report by email with script logs
  if (sendReport) {
    var reportBody = Logger.getLog();
    GmailApp.sendEmail(reportRecipient, reportTitle, reportBody);
  }
}