dropdownlist之间的互相联动实现（显示与隐藏）

<script language="javascript" type ="text/javascript" > var Arrchange1 =new Array (); 
var Arrchange2 =new Array (); 
var Arrchange3 =new Array (); 
function hide(s_id,index) 
{ 
var xxx = document .getElementById (s_id); 
var oldOption = xxx.children(index); 
var oldStr = oldOption.innerText; 
var newOption = document.createElement('<div' + oldOption.outerHTML.match(/(<\w*)([^>]*)(>)/)[2] +'>'); 
newOption.innerText= oldStr; 
newOption.swapNode(oldOption); 
//alert(xxx.innerHTML); 
} 
function show(s_id,index) 
{ 
var xxx =document .getElementById (s_id); 
var oldOption = xxx.children(index); 
if(oldOption.tagName=='DIV') 
{ 
var oldStr = oldOption.innerText; 
var newOption = document.createElement('<option' + oldOption.outerHTML.match(/(<\w*)([^>]*)(>)/)[2] +'>'); 
newOption.innerText = oldStr; 
newOption.swapNode(oldOption); 
} 
//alert(xxx.innerHTML); 
} 

function onchange1() 
{ 
var s_index=document .getElementById ("Ddl_question1").options[document .getElementById ("Ddl_question1").selectedIndex].value; 
s_index = parseInt(s_index); 
if(s_index ==0) 
{ 
show ('Ddl_question2',Arrchange1 [0] ); 
show ('Ddl_question3',Arrchange1 [0] ); 
Arrchange1.pop(); 
} 
else 
{ 
Arrchange1.push(s_index); 
if(Arrchange1.length>0) 
{ 
show ('Ddl_question2',Arrchange1 [0] ); 
} 
if(Arrchange1.length>0) 
{ 
show ('Ddl_question3',Arrchange1 [0] ); 
} 
hide('Ddl_question2',s_index); 
hide('Ddl_question3',s_index); 
} 
} 
function onchange2() 
{ 
var s_index=document .getElementById ("Ddl_question2").options[document .getElementById ("Ddl_question2").selectedIndex].value; 
s_index = parseInt(s_index); 
if(s_index ==0) 
{ 
show ('Ddl_question1',Arrchange1 [0] ); 
show ('Ddl_question3',Arrchange3 [0] ); 
Arrchange2.pop(); 
} 
else 
{ 
Arrchange2.push(s_index); 
if(Arrchange2.length>0) 
{ 
show ('Ddl_question1',Arrchange2 [0] ); 
} 
if(Arrchange2.length>0) 
{ 
show ('Ddl_question3',Arrchange2 [0] ); 
} 
hide('Ddl_question1',s_index); 
hide('Ddl_question3',s_index); 
} 
} 
function onchange3() 
{ 
var s_index=document .getElementById ("Ddl_question3").options[document .getElementById ("Ddl_question3").selectedIndex].value; 
s_index = parseInt(s_index); 
if(s_index ==0) 
{ 
show ('Ddl_question1',Arrchange3 [0] ); 
show ('Ddl_question2',Arrchange3 [0] ); 
Arrchange3.pop(); 
} 
else 
{ 
Arrchange3.push(s_index); 
if(Arrchange1.length>0) 
{ 
show ('Ddl_question1',Arrchange3 [0] ); 
} 
if(Arrchange2.length>0) 
{ 
show ('Ddl_question2',Arrchange3 [0] ); 
} 
hide('Ddl_question1',s_index); 
hide('Ddl_question2',s_index); 
} 
} 
function a() {alert("fuck ");} 
</script> 
<select name="Ddl_question1" id="Ddl_question1" onchange="onchange1()"> 
<option value="0">请选择密保信息</option> 
<option value="1">您母亲的姓名是？</option> 
<option value="2">您父亲的姓名是？</option> 
<option value="3">您配偶的姓名是？</option> 
<option value="4">您的出生地是？</option> 
<option value="5">您高中班主任的姓名是？</option> 
<option value="6">您初中班主任的姓名是？</option> 
<option value="7">您小学班主任的姓名是？</option> 
<option value="8">您小学校名是？</option> 
<option value="9">您的学号(或工号)是？</option> 
<option value="10">您父亲的生日是？</option> 
<option value="11">您母亲的生日是？</option> 
<option value="12">您配偶的生日是？</option> 
</select> 
<select name="Ddl_question2" id="Ddl_question2" onchange="onchange2()"> 
<option value="0">请选择密保信息</option> 
<option value="1">您母亲的姓名是？</option> 
<option value="2">您父亲的姓名是？</option> 
<option value="3">您配偶的姓名是？</option> 
<option value="4">您的出生地是？</option> 
<option value="5">您高中班主任的姓名是？</option> 
<option value="6">您初中班主任的姓名是？</option> 
<option value="7">您小学班主任的姓名是？</option> 
<option value="8">您小学校名是？</option> 
<option value="9">您的学号(或工号)是？</option> 
<option value="10">您父亲的生日是？</option> 
<option value="11">您母亲的生日是？</option> 
<option value="12">您配偶的生日是？</option> 
</select> 
<select name="Ddl_question3" id="Ddl_question3" onchange="onchange3()"> 
<option value="0">请选择密保信息</option> 
<option value="1">您母亲的姓名是？</option> 
<option value="2">您父亲的姓名是？</option> 
<option value="3">您配偶的姓名是？</option> 
<option value="4">您的出生地是？</option> 
<option value="5">您高中班主任的姓名是？</option> 
<option value="6">您初中班主任的姓名是？</option> 
<option value="7">您小学班主任的姓名是？</option> 
<option value="8">您小学校名是？</option> 
<option value="9">您的学号(或工号)是？</option> 
<option value="10">您父亲的生日是？</option> 
<option value="11">您母亲的生日是？</option> 
<option value="12">您配偶的生日是？</option> 
</select>