extjs4 grid 合并单元格

//传入要合并的grid，和要合并的列，cloArr为数组，如[0,1,2]    
function  mergeCells(grid, colArr){
    var gridNextTd;

    var n=0;//n是 始终记住要合并单元格的第一个值的标志
    var currentTdValue;//要合并起始单元格的值
    var currentTd;   //当前单元格
    var preTdValue; //前一个单元格的值
    var preCurrentTdValue;// 要合并起始单元格的前一个值
    //找到grid的所有行
    var gridTrArr = document.getElementById(grid.getId() + "-body").firstChild.firstChild.getElementsByTagName("tr");
    //循环要合并的列
    for (var j = 0; j < colArr.length; j++) {
        var count= 0;
        //遍历grid的所有行
        for (var i = 0; i < gridTrArr.length; i++) {
            //查找grid某一行的所有列
            var gridTdArr = gridTrArr[i].getElementsByTagName("td");
            if(colArr[j]>0){
                //var preGridTdArr=gridTrArr[i-1].getElementsByTagName("td");
                //获取当前单元格，前一列的值
                preCurrentTdValue=gridTdArr[colArr[j]-1].getElementsByTagName("div")[0].textContent;
            }
            //记住要合并的第一个单元格的值
            if(n==i){
                currentTd=gridTdArr[colArr[j]];
                currentTdValue= gridTdArr[colArr[j]].getElementsByTagName("div")[0].textContent;
                if(colArr[j]>0){
                    preTdValue = gridTdArr[colArr[j]-1].getElementsByTagName("div")[0].textContent;
                }
                count++;
                continue;
            }
            //获取这一行中要合并的这一列的值
            var gridTdValue=gridTdArr[colArr[j]].getElementsByTagName("div")[0].textContent;
            if(currentTdValue===gridTdValue){
                //若是本列中，这两行相等，前一列中，这两行不相等，则不应该合并
                if(preTdValue==null||preTdValue===preCurrentTdValue){
                    gridTdArr[colArr[j]].style.display="none";
                    count++;
                }
                //若是不相等，则合以上的单元格
                else{
                    currentTd.rowSpan=count;
                    currentTd.style.verticalAlign="middle";
                    n=i;
                    i--;
                    count=0;
                }
                //第一页合并完毕
                if(i==gridTrArr.length-1){
                    //第二页n清0
                    n=0;
                    currentTd.rowSpan=count;
                    currentTd.style.verticalAlign="middle";
                }
            }else{
                n=i;
                //比较最后一次，i会自动+1,所以此处减一
                i--;
                //若是本列中，这两行相等，前一列中，这两行不相等，则不应该合并,判断null是为了，复选框的情况
//                if(preTdValue==null||preTdValue===preCurrentTdValue) {
                    currentTd.rowSpan = count;
                    currentTd.style.verticalAlign = "middle";
//                }
                //count清0
                count = 0;
            }
        }
    }
}