<table id="table">
<tr>
<td>1</td>
</tr>
<tr>
<td>2</td>
</tr>
<tr>
<td>3</td>
</tr>
</table>
获取tr元素的个数:
$("#table tr").length
<table id="table">
<tr>
<td>1</td>
</tr>
<tr>
<td>2</td>
</tr>
<tr>
<td>3</td>
</tr>
</table>
获取tr元素的个数:
$("#table tr").length