javaScript DOM

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>添加单元格</title>
    <script type="text/javascript">
            var count = 0;

            function addRow() {
                //创建文本结点
                if(count < 0){
                    count = 0;
                }
                count++;
                var textNode1 = document.createTextNode("单元格"+count);
                var textNode2 = document.createTextNode("单元格"+count)
                var textNode3 = document.createTextNode("单元格"+count)
                //创建td的元素结点
                var tdNode1 =  document.createElement("td");
                var tdNode2 =  document.createElement("td");
                var tdNode3 =  document.createElement("td");

                var trNode = document.createElement("tr");
                //将文本节点添加到td的元素结点
                tdNode1.appendChild(textNode1);
                tdNode2.appendChild(textNode2);
                tdNode3.appendChild(textNode3);
                //获取tr 和 table 的 结点元素
                var tbNode = document.getElementById("tb") ;
                //将td结点添加到 tr结点   tr 添加到table
                trNode.appendChild(tdNode1);
                trNode.appendChild(tdNode2);
                trNode.appendChild(tdNode3);
                tbNode.appendChild(trNode);
                if(count%2==1){
                    trNode.style.backgroundColor = "#f5c7ff";
                }

            };

            function delRow() {
                var tbNode = document.getElementById("tb") ;
                tbNode.removeChild(tbNode.lastChild);
                count--;
            }

    </script>
</head>
<body>
<input type="button" value="新增一行" onclick="addRow();" />
<input type="button" value="删除一行" onclick="delRow();" />
<hr />
    <table id="tb" width="500px" border="1" cellpadding="0" cellspacing="0" >
       <!-- <tr id = "tr">
            <td id="td1">单元格1</td>
            <td id="td2">单元格2</td>
            <td id="td3">单元格3</td>
        </tr>-->
    </table>

</body>
</html>
这里写图片描述
鲜花会生锈，盐巴会腐烂