Sort history by date due

//Sort history by date due

  var colIndex_circHist_dateDue = $('#pat_readingrec th:contains("Date due")').index();

  if (window.location.href.indexOf("readingrec.pl") > -1) {
    $(window).load(function () {
      var table = $('#table_readingrec').DataTable();
      // Sort by date due column and then re-draw
      table
          .order( [ colIndex_circHist_dateDue, 'desc' ] )
          .draw();
    });
  }