Google Apps Script - Delete all contact groups

deletecontactgroups.gs

function deleteContactGroups() {
  var groups = ContactsApp.getContactGroups();

  Logger.log("total: " + groups.length);
  for (var i = 0; i < groups.length; i++) {
    if (!groups[i].isSystemGroup()){
      groups[i].deleteGroup()
      Logger.log("deleting: " + groups[i].getName() );
    }
  }
}