JS为table动态增加行

<script language="javascript" type="text/javascript">
function insRow() {
var x = document.getElementById('abcd').insertRow(1)
var a = x.insertCell(0)
var b = x.insertCell(1)
}

<table border="1" runat="server" id="abcd">
<tr >
<td>
<input type="button" onclick="insRow()" value="插入行">
</td>

<td colSpan=2>8</td>
<td colSpan=2>9</td>
<td colSpan=2>10</td>
<td colSpan=2>11</td>
<td colSpan=2>12</td>
<td colSpan=2>13</td>
<td colSpan=2>14</td>
<td colSpan=2>15</td>
<td colSpan=2>16</td>
<td colSpan=2>17</td>
<td colSpan=2>18</td>
<td colSpan=2>19</td>
<td colSpan=2>20</td>
</tr>
<tr>
<td></td>
<TD> </td>
<TD> </td>
<TD> </td>
<TD> </TD>
<TD> </TD>
<TD> </TD>
<TD> </TD>
<TD> </TD>
<TD> </TD>
<TD> </TD>
<TD> </TD>
<TD> </TD>
<TD> </TD>
<TD> </TD>
<TD> </TD>
<TD> </TD>
<TD> </TD>
<TD> </TD>
<TD> </TD>
<TD> </TD>
<TD> </TD>
<TD> </TD>
<TD> </TD>
<TD> </TD>
<TD> </TD>
<TD> </TD>
</tr>

</table>