jQuery选择器中使用css选择器的语法

    <table>
        <tr>
            <td>row1 col1</td>
            <td>row1 col2</td>
            <td>row1 col3</td>
        </tr>
        <tr>
            <td>row2 col1</td>
            <td>row2 col2</td>
            <td>row2 col3</td>
        </tr>
        <tr>
            <td>row3 col1</td>
            <td>row3 col2</td>
            <td>row3 col3</td>
        </tr>
        <tr>
            <td>row4 col1</td>
            <td>row4 col2</td>
            <td>row4 col3</td>
        </tr>
        <tr>
            <td>row5 col1</td>
            <td>row5 col2</td>
            <td>row5 col3</td>
        </tr>
    </table>

<script type="text/javascript">
    console.log($('table').find('tr').eq(2).find('td').eq(2).html());
    console.log($('table tr:eq(2) td:eq(2)').html());
    console.log($('table tr:nth-of-type(3) td:nth-of-type(3)').html());
    console.log($('table tr td:nth-of-type(3)').length);
    console.log($('table tr td:eq(2)').length);
</script>