javascript怎么实现动态在某个<tr></tr>标签添加父标签。

javascript怎么实现动态在某个<tr></tr>标签添加父标签。<table id="tab1" border="1">
<tr>
<td>A</td>
<td>B</td>
</tr> <tr>
<td>A1</td>
<td>B1</td>
</tr> <tr>
<td>A2</td>
<td>B2</td>
</tr>
<tr>
<td>A3</td>
<td>B3</td>
</tr></table>怎么在第N个<tr></tr>添加父标签<thead>如想在A,B的<tr></tr>上添加成
<thead>
  <tr>
     <td>A</td>
     <td>A</td>
  </tr>
</thead>
或者在 A3,A4上添加成
<tfood>
  <tr>
     <td>A3</td>
     <td>A4</td>
  </tr>
</tfood>

解决方案 »

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搞半天才发现你这个需求实现不了，浏览器会自动创建tbody对象，并把所有的行添加到tbody对象中。导致在tbody对象中添加thead或tfoot对象，这个操作是非法的。
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<script type="text/javascript">
function wrap(id, tag, index, wrapperTag) {
var obj = document.getElementById(id);
var targetObj = obj.getElementsByTagName(tag)[index]; //待操作的目标对象
var cloneObj = targetObj.cloneNode(true); //克隆一遍
var wrapper = document.createElement(wrapperTag); //创建指定的父标签
wrapper.appendChild(cloneObj); //把克隆得来的对象插入wrapper节点
obj.insertBefore(wrapper, targetObj); //把wrapper节点添加到目标对象前面
obj.removeChild(targetObj); //删除目标节点
}window.onload = function() {
wrap('demo', 'p', 1, 'div');  //成功
wrap('tab1', 'tr', 0, 'thead');  //失败
}
</script>
</head><body>
    <table id="tab1" border="1">
        <tr>
            <td>A</td>
            <td>B</td>
        </tr>
        <tr>
            <td>A1</td>
            <td>B1</td>
        </tr>
        <tr>
            <td>A2</td>
            <td>B2</td>
        </tr>
        <tr>
            <td>A3</td>
            <td>B3</td>
        </tr>
    </table>

    <div id="demo">
     <p>第一行</p>
        <p>第二行</p>
        <p>第三行</p>
    </div>
</body>
</html>
thead、tfoot要么不用，用了就必须同时使用thead、tbody、tfoot标签对表格行进行分组。如果你只是想把表格的最前面的一行或几行套上thead标签，同时把表格最后的一行或几行套上tfoot标签，这是可以做到的。
    我就只是想前N行套上thead标签而已。
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<style type="text/css">
thead { color:red; }
</style>
<script type="text/javascript">
window.onload = function() {
//前2行套上thead标签
var table = document.getElementById('tab1');
var row_01 = table.getElementsByTagName('tr')[0];
var row_02 = table.getElementsByTagName('tr')[1];
var cloneRow_01 = row_01.cloneNode(true);
var cloneRow_02 = row_02.cloneNode(true);
var thead = document.createElement('thead');
var tbody = table.getElementsByTagName('tbody')[0];
thead.appendChild(cloneRow_01);
thead.appendChild(cloneRow_02);
tbody.removeChild(row_01);
tbody.removeChild(row_02);
table.insertBefore(thead, tbody);
}
</script>
</head><body>
    <table id="tab1" border="1">
        <tr>
            <td>A</td>
            <td>B</td>
        </tr>
        <tr>
            <td>A1</td>
            <td>B1</td>
        </tr>
        <tr>
            <td>A2</td>
            <td>B2</td>
        </tr>
        <tr>
            <td>A3</td>
            <td>B3</td>
        </tr>
    </table>
</body>
</html>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title><script type="text/javascript">
window.onload = function() {
    //前2行套上thead标签
    var table = document.getElementById('tab1');    var row_01 = table.getElementsByTagName('tr')[0];
    var row_02 = table.getElementsByTagName('tr')[1];
var row_03 = table.getElementsByTagName('tr')[3];    var cloneRow_01 = row_01.cloneNode(true);
    var cloneRow_02 = row_02.cloneNode(true);
var cloneRow_03 = row_02.cloneNode(true);    var thead = document.createElement('thead');
    var tbody = table.getElementsByTagName('tbody')[0];
    thead.appendChild(cloneRow_01);
    thead.appendChild(cloneRow_02);
    tbody.insertBefore(thead,row_01);
tbody.removeChild(row_01);
    tbody.removeChild(row_02); alert(table.outerHTML);
}
</script>
</head><body>
    <table id="tab1" border="1">
        <tr>
            <td>A</td>
            <td>B</td>
        </tr>
        <tr>
            <td>A1</td>
            <td>B1</td>
        </tr>
        <tr>
            <td>A2</td>
            <td>B2</td>
        </tr>
        <tr>
            <td>A3</td>
            <td>B3</td>
        </tr>
    </table>
</body>
</html>
安照你的方法，确实可以添加到THEAD \TFOOD
但页面表格的显示却变了，为什么会这样？