我想遍历table中第二列中所有单元格如何写呢

Question

<script>
function get()
{
obj=document.all.tb
alert(obj.rows[0].cells[1].innerText)
alert(obj.rows[1].cells[1].innerText)
alert(obj.rows[2].cells[1].innerText)
}
</script>
<table id=tb border=1 width=100 height=100>
<tr><td>1</td><td>2</td><td>3</td></tr>
<tr><td>4</td><td>5</td><td>6</td></tr>
<tr><td>7</td><td>8</td><td>9</td></tr>
</table>
<input type="button" value="test" onclick="get()">

Answer 1

<TABLE id="tb1">
<TR>
<TD>a</TD>
<TD>b</TD>
<TD>c</TD>
</TR>
<TR>
<TD>A</TD>
<TD>B</TD>
<TD>C</TD>
</TR>
<TR>
<TD>1</TD>
<TD>2</TD>
<TD>3</TD>
</TR>
</TABLE>
<script language="javascript">
var tb1=document.getElementById("tb1");
for(i=0;i<tb1.rows.length;i++){
alert(tb1.rows[i].cells[1].innerText);
}
</script>