关于获取当前所在tr的问题

Question

<table>
        <tr>
            <td>
            </td>
            <td>
            </td>
            <td>
            </td>
        </tr>
        <tr>
            <td>a
            </td>
            <td>b
            </td>
            <td>c
            </td>
            <td>
                <a onclick="a(this)">121212</a>
            </td>
            <td>e
            </td>
        </tr>
    </table>    <script>
    function a(obj){         
        var tr=obj.parentElement.parentElement;        
        tr.children[1].innerHTML="11";
    } </script>

Answer 1

<table border="1">
<tr>
<td></td><td></td><td></td>
</tr>
<tr>
<td></td><td></td><td></td><td><a onclick="this.parentNode.previousSibling.innerHTML='www'">dddd</td><td></td>
</tr>
</table>