Delete gmail emails which matches filter

purgeGmail

function purgeMail() {
  var GMAIL_LABELS = "label1, label2, label3";
  var PURGE_SIZE = 0
  var PURGE_DATE = "2010-01-01"

  GmailApp.moveThreadsToTrash(
     GmailApp.search(GMAIL_LABELS
                      .split(',')
                      .map(function (e) {return "label:" + e.trim();})
                      .join('|') + " size:" + PURGE_SIZE.toString() + " before:" + PURGE_DATE));
}