好心人请来看看，帮我。

Question

<SCRIPT LANGUAGE="JavaScript" >
<!--
   function test1(){
     var a=document.getElementsByTagName("div")
     for(i=0;i<a.length;i++)
     {
        alert(a[i].id)
     }
   }
   function test2(){
     var b=document.getElementsByTagName("TD")
     for(i=0;i<b.length;i++)
     {
        alert(b[i].id)
     }
   }//-->
</SCRIPT> <table id="table1" border="1">
  <tr>
    <td width="100" align="center">
        <TABLE id="table11" border="1">
        <TR>
         <TD id="td1"><DIV id="d1" class="child1">d1</div></TD>
         <TD id="td1"><DIV id="d2" class="child2">d2</div></TD>
        </TR>
        </TABLE>
    </td>
    <td width="100" align="center">        <TABLE id="table22" border="1">
        <TR>
         <TD id="td11"><DIV id="ddd1" class="child1">d22</div></TD>
         <TD id="td22"><DIV id="ddd2" class="child2">d33</div></TD>
        </TR>
        </TABLE>    </td>
  </tr>
</table><INPUT TYPE="button" onclick="test1();" value="test1">
<INPUT TYPE="button" onclick="test2();" value="test2">

Answer 1

document.getElementById("table22").getElementByTagName("div")document.getElementById("table1").getElementByTagName("table")

Answer 2

加一个判断条件<SCRIPT LANGUAGE="JavaScript" >
<!--
   function test1(){
     var a=document.getElementsByTagName("div")
     for(i=0;i<a.length;i++)
     {
        if(a[i].id!="")
        alert(a[i].id)
     }
   }
   function test2(){
     var b=document.getElementsByTagName("TD")
     for(i=0;i<b.length;i++)
     {
        if(b[i].id!="") 
        alert(b[i].id)
     }
   }//-->
</SCRIPT>

Answer 3

<table id="table1" border="1">
  <tr>
    <td width="100" align="center">
        <TABLE id="table11" border="1">
        <TR>
         <TD id="td1"><DIV id="d1" class="child1">d1</div></TD>
         <TD id="td1"><DIV id="d2" class="child2">d2</div></TD>
        </TR>
        </TABLE>
    </td>
    <td width="100" align="center">        <TABLE id="table22" border="1">
        <TR>
         <TD id="td11"><DIV id="ddd1" class="child1">d22</div></TD>
         <TD id="td22"><DIV id="ddd2" class="child2">d33</div></TD>
        </TR>
        </TABLE>    </td>
  </tr>
</table>
<input type="button" value=" Click Me To View " onclick="ViewTheInfo()" />
<script language="javascript">function ViewTheInfo()
{
var eleDiv=document.getElementById("table22").getElementsByTagName("div")
alert(eleDiv.length);
for(i=0;i<eleDiv.length;i++)
{
if(eleDiv[i].id!="")
{
alert(eleDiv[i].id);
}
}

var eleTable=document.getElementById("table1").getElementsByTagName("table")
alert(eleTable.length);
for(i=0;i<eleTable.length;i++)
{
if(eleTable[i].id!="")
{
alert(eleTable[i].id);
}
}
}
</script>