关联菜单！

<form method=post name=fm>
<select onchange=chg(selectedIndex) name=a>
<option>亚洲
<option>欧洲
<option>美洲
</select>
<select name=b onchange="r.value=value">
<option>请选择
</select>
<input name=r id=r>
</form>
<script>
var arr=[["中国","日本","朝鲜","新加坡"],["英国","法国","意大利"],["美国","加拿大","巴西"]]
function chg(i){
with(document.fm.b){
length=0;
for(j=0;j<arr[i].length;j++)
options.add(new Option(arr[i][j],arr[i][j]))
document.fm.r.value=value+document.fm.a.value
}
}
chg(0)
</script>

解决方案 »

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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
<TITLE> New Document </TITLE>
<META NAME="Generator" CONTENT="EditPlus">
<META NAME="Author" CONTENT="">
<META NAME="Keywords" CONTENT="">
<META NAME="Description" CONTENT="">
<script language="JavaScript" type="text/javascript">

</script>
</HEAD><BODY>
<FORM name="testform" id="testform">
<select id=province
      onchange=show_city(this.options.selectedIndex)>
<OPTION value="" selected>请选择类别</option>
</select>
<select id=city>
    <OPTION value="" selected>请选择专业</OPTION>
</select>
<select id=city1>
    <OPTION value="" selected>请选择专业</OPTION>
</select>
</FORM>
</BODY>
</HTML>
1.多级关联菜单(一)
<BODY>
<SELECT NAME="s1"><option>需要JavaScript才能正确显示</SELECT>
<SELECT NAME="s2"></SELECT>
<SELECT NAME="s3"></SELECT>
<SELECT NAME="s4"></SELECT>
<SCRIPT LANGUAGE="JavaScript">

</SCRIPT>
</BODY>
</HTML>
２．多级连动(二)
<select name=year></select>
<select name=month></select>
<select name=date></select>
<select name=clock></select>
<input name=result>
<script>
var arrSel=["year","month","date","clock"];//arrSel定义了要修改的下拉框和xml数据的节点名称
</script>
<xml id=xmldata>
<xmldata>
  <year value="2000">
   <month value="4">
    <date value="14">
     <clock value="一点" />
     <clock value="三点" />
    </date>
    <date value="17">
     <clock value="一点" />
    </date>
   </month>
   <month value="5">
    <date value="15">
     <clock value="一点" />
     <clock value="四点" />
     <clock value="七点" />
    </date>
   </month>
  </year>
  <year value="2001">
   <month value="7">
    <date value="16">
     <clock value="一点" />
     <clock value="五点" />
     <clock value="九点" />
    </date>
   </month>
  </year>
</xmldata>
</xml>
<script>
function qswhXml(num){
/******* by qiushuiwuhen(2002-5-17) ********/
var i,j,arrTemp=[];
for(i=0;i<num;i++)arrTemp[i]=document.all(arrSel[i]).options[document.all(arrSel[i]).selectedIndex].text
if(num==arrSel.length){//这里处理最后的数据。
  document.all("result").value="选中了("+arrTemp+")";return;
}
with(document.all(arrSel[num])){
  length=0
  var obj=document.all.xmldata.XMLDocument.childNodes[0];
  for(i=0;i<num;i++)obj=obj.selectSingleNode(arrSel[i]+'[@value="'+arrTemp[i]+'"]');
  for(i=0;i<obj.childNodes.length;i++)options[length++].text=obj.childNodes[i].getAttribute("value");
  onchange=new Function("qswhXml("+(num+1)+")");
  onchange();
}
}
qswhXml(0);
</script>
３．多级连动(三)
<select name=one></select>
<select name=two></select>
<select name=three></select>
<select name=four></select>
<input name=result><script>
var arrSel=["one","two","three","four"];//arrSel定义了要修改的下拉框
var i=0,arrData=[];//arrData中搁的是数据,每条都显示各级的数据
arrData[i++]=["2000","4","14","一点"]
arrData[i++]=["2000","4","14","二点"]
arrData[i++]=["2000","4","18","三点"]
arrData[i++]=["2000","7","14","二点"]
arrData[i++]=["2001","6","15","二点"]
arrData[i++]=["2001","6","23","七点"]
arrData[i++]=["2001","8","18","二点"]
arrData[i++]=["2002","7","1","二点"]
arrData[i++]=["2002","7","1","三点"]
arrData[i++]=["2002","7","11","二点"]
arrData[i++]=["2002","7","19","二点"]
</script>
<script>
function qswhInit(num){
/******* by qiushuiwuhen(2002-5-15) ********/
var i,j,arrTemp=[];
for(i=0;i<num;i++)arrTemp[i]=document.all(arrSel[i]).options[document.all(arrSel[i]).selectedIndex].text
if(num==arrSel.length){//这里处理最后的数据。
document.all("result").value="选中了("+arrTemp[0]+","+arrTemp[1]+","+arrTemp[2]+","+arrTemp[3]+")";return;
}
with(document.all(arrSel[num])){
length=0
for(i=0;i<arrData.length;i++){
for(j=0;j<num;j++)if(arrTemp[j]!=arrData[i][j])break;
if(j!=num)continue;
if(length==0||options[length-1].text!=arrData[i][num])
options[length++].text=arrData[i][num];
}
onchange=new Function("qswhInit("+(num+1)+")");
onchange();
}
}
qswhInit(0);//初始化
</script>
asp.net里面用web service做，比较灵活，容易控制。