基于css样式绑定的样式驱动式AJAX程序开发（.net实现）

基于css样式绑定的样式驱动式AJAX程序开发（.net实现）(31)         if (null == previousSortOrder '' == previousSortOrder 'DESC' == previousSortOrder) ...{
            spanEl.appendChild(document.createTextNode(' ↑'));
            td.setAttribute('sortOrder', 'ASC');
            spanEl.setAttribute('sortOrder', 'ASC');
        } else ...{
            spanEl.appendChild(document.createTextNode(' ↓'));
            td.setAttribute('sortOrder', 'DESC');
            spanEl.setAttribute('sortOrder', 'DESC');
        }
            td.appendChild(spanEl);

        // 以下为没有doPostBack的版本,已经取消
        /**//*
            if(td.firstChild.getAttribute('columnId')!=null) {       
                window.location = "?sortdirect="+td.getAttribute('sortOrder')+"&colid="+td.firstChild.getAttribute('columnId');
            }
            else {           
                  window.location = "?sortdirect="+td.getAttribute('sortOrder')+"&colid="+td.getAttribute('columnId');
             }