不太想描述，大家自行理解吧，這樣可能記憶會深一點兒～

<script type="text/javascript">
function mergeCells(){
    var count = 0;
    var oldText = '';
    var oldTd;
    var count2 = 0;
    var oldText2 = '';
    var oldTd2;
    var isDelete = false;
    var trs = document.getElementsByTagName("tr");
    for ( var i = 0; i < trs.length; i++) {
        
 
var tds = trs[i].getElementsByTagName("td");
        if(count == 0){
            oldText = tds[0].innerHTML;
            oldTd = tds[0];
            count = 1;
        }else if(oldText != tds[0].innerHTML){
            oldTd.rowSpan = count;
            oldText =  tds[0].innerHTML;
            oldTd = tds[0];
            count 
 
= 1;
        }else{
            count = count + 1;
            tds[0].parentNode.removeChild(tds[0]);
            isDelete = true;
        }
        if(i == trs.length - 1){
            oldTd.rowSpan = count;
        }
        
        /*添加了一個isDelete變數,用於判斷是否刪除元素*/
        if(count2 == 0){
            oldText2 
 
= tds[1].innerHTML;
            oldTd2 = tds[1];
            count2 = 1;
        }else if(isDelete){
             if(oldText2 != tds[0].innerHTML){
                oldTd2.rowSpan = count2;
                oldText2 =  tds[0].innerHTML;
                oldTd2 = tds[0];
                count2 = 1;
                }else{
                    count2 = count2 + 1;
                    tds[1].parentNode.removeChild(tds[0]);
                }
             isDelete = false;
        }else{
             if(oldText2 != tds[1].innerHTML){
                oldTd2.rowSpan = count2;
                oldText2 =  tds[1].innerHTML;
                oldTd2 = tds[1];
                count2 = 1;
                }else{
                    count2 = count2 + 1;
                    tds[1].parentNode.removeChild(tds[1]);
                }
        }
        if(i == trs.length - 1){
            oldTd2.rowSpan = count2;
        }
    }
}
mergeCells();
</script>