IE下cloneNode(true)一个TR取其.cells[index]报 'cells.[index].firstChild'为空或不是对象

下列js代码，报“'cells.4.firstChild'为空或不是对象”：

var templateRow = copiedTable.firstChild.lastChild;
var newRow = templateRow.cloneNode(true);
newRow.style.display = "block";
var refRow = copiedTable.firstChild.firstChild.nextSibling //insertBefore()的参照行

///alert(newRow.cells[4])  ////为“undefined”
newRow.cells[4].firstChild.value = curSrcRow.cells[4].firstChild.nodeValue;
            
///set curSrcRow's values to newRow
copyPloValues(newRow, curSrcRow);

///插入新行
if(refRow) {
    copiedTable.firstChild.insertBefore(newRow, refRow);
} else {
    copiedTable.firstChild.appendChild(newRow);
}

得知，IE下(firefox/opera/chrome下无此问题，见下面的链接二)，cloneNode(true)克隆出的table的tr，在未插入到DOM tree成为其一部分之前，其cells[]是不可用的。(In IE，It turns out that the .cells[] accessor is only available after you append the row into the DOM tree)

参见：
.rows[] and .cells[] in IE when using cloneNode()：
http://jehiah.cz/a/rows-and-cells-in-ie-when-using-clonenode
A cloned (cloneNode) table row element (<tr>) stops beeing a table row element in IE：
http://www.reingroot.nl/bugreports/js/javascript/cloneRowInIE.html

解决办法正如上述链接一所述，调换新行插入代码（insertBefore()/appendChild()）与取新行cells[]代码块的顺序：

var templateRow = copiedTable.firstChild.lastChild;
var newRow = templateRow.cloneNode(true);
newRow.style.display = "block";
var refRow = copiedTable.firstChild.firstChild.nextSibling //insertBefore()的参照行
            
///set curSrcRow's values to newRow
copyPloValues(newRow, curSrcRow);

///插入新行
if(refRow) {
    copiedTable.firstChild.insertBefore(newRow, refRow);
} else {
    copiedTable.firstChild.appendChild(newRow);
}

//alert(newRow.cells[4] + ' ' + newRow.cells[4].nodeName);  ////为“[object] TD”
newRow.cells[4].firstChild.value = curSrcRow.cells[4].firstChild.nodeValue;