一个小问题

Question

<table id="table1" border="1" cellpadding="0" cellspacing="0" width="100%">
    <tr id="1">
        <td id="2" width="10%"><input type="button" id="btn1" value="Click" onclick="alert(this.parentNode.id);alert(this.parentNode.parentNode.id)"></td>
        <td id="3" width="90%">&nbsp;</td>
    </tr>
</table>

Answer 1

<table id="table1" border="1" cellpadding="0" cellspacing="0" width="100%">
    <tr id="1">
        <td id="2" width="10%"><input type="button" id="btn1" value="Click" onclick="aa(this);"></td>
        <td id="3" width="90%">&nbsp;</td>
    </tr>
</table><script>
function aa(obj){
alert(obj.parentNode.id);
alert(obj.parentNode.parentNode.id); 
}</script>