JavaScript获取表格（table）的行数和列数

如何使用JavaScript获取表格（table）的行数和列数？其实很简单，假设存在如下表格：

<table width="100%" border="1" cellspacing="0" cellpadding="0" id="example_table">
    <tr>
        <td>&nbsp;</td>
        <td>&nbsp;</td>
        <td>&nbsp;</td>
        <td>&nbsp;</td>
        <td>&nbsp;</td>
    </tr>
    <tr>
        <td>&nbsp;</td>
        <td>&nbsp;</td>
        <td>&nbsp;</td>
        <td>&nbsp;</td>
        <td>&nbsp;</td>
    </tr>
    <tr>
        <td>&nbsp;</td>
        <td>&nbsp;</td>
        <td>&nbsp;</td>
        <td>&nbsp;</td>
        <td>&nbsp;</td>
    </tr>
</table>

则获取该表格的行数和列数可分别如下代码：

//表格行数
var rows = document.getElementById("example_table").rows.length;

//表格列数
var cells = document.getElementById("example_table").rows.item(0).cells.length;