Sorting remove existing css classes

[Yoruba]

Maybe you can add this code to fix the remove existing css classes?
(I'm not a JavaScript developer so maybe there is a better way to fix this.)
Thanks.

            if (that.prevCol === that.column) {
                // if already sorted, reverse
                // th.className = th.className !== 'descend' ? 'descend' : 'ascend';
                th.classList.toggle('ascend');
                th.classList.toggle('descend');
                that.reverseTable();
            }
            else {
                // not sorted - call quicksort
                th.classList.toggle('descend');
                if (that.prevCol !== -1 && that.ths[that.prevCol].className !== 'exc_cell') {
                    // that.ths[that.prevCol].className = '';
                    that.ths[that.prevCol].classList.remove('descend', 'ascend');
                }
                that.quicksort(0, that.trs.length);
            }