Javascript 操作合并table列rowspan

<script language="JavaScript">
        function rowSpans_Cells(tab) {
            var maxCol = 5, val, count, start;  //maxCol：合并单元格作用到多少列    
            for (var col = maxCol - 1; col >= 0; col--) {
                count = 1;
                val = "";
                for (var i = 0; i < tab.rows.length; i++) {
                    if (val == tab.rows[i].cells[col].innerHTML) {
                        count++;
                    } else {
                        if (count > 1) { //合并
                            start = i - count;
                            tab.rows[start].cells[col].rowSpan = count;
                            for (var j = start + 1; j < i; j++) {
                                tab.rows[j].cells[col].style.display = "none";
                            }
                            count = 1;
                        }
                        val = tab.rows[i].cells[col].innerHTML;
                    }
                }
                if (count > 1) { //合并，最后几行相同的情况下
                    start = i - count;
                    tab.rows[start].cells[col].rowSpan = count;
                    for (var j = start + 1; j < i; j++) {
                        tab.rows[j].cells[col].style.display = "none";
                    }
                }
            }

        }
        rowSpans_Cells(tb_qk);
    </script>

此代码是转载.