js实现的selece二级联动(简单实用)

以下是html代码:
<!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="">
 </HEAD>
<!-- by sundful  starting-->
 <BODY>
  <script   language="JavaScript">     
     
  var   subcat   =   new   Array();     
  subcat[0]   =   new   Array('中文','英语','英语')     
  subcat[1]   =   new   Array('中文','法语','法语')        
  subcat[2]   =   new   Array('英语','中文','中文')     
  subcat[3]   =   new   Array('法语','中文','中文')         
  function   changeselect1(locationid)     
  {     
  document.form1.s2.length   =   0;   //初始化下拉列表   清空下拉数据     
  document.form1.s2.options[0]   =   new   Option('==请选择==','');   //给第一个值     
  for   (i=0;   i<subcat.length;   i++)   //legth=20     
  {     
  if   (subcat[i][0]   ==   locationid)   //[0]   [1]   第一列   第二列     
  {document.form1.s2.options[document.form1.s2.length]   =   new   Option(subcat[i][1],   subcat[i][2]);}   //建立option     
  //第一次   length=1   因为有==请选择==     
  //i=9时   length=   10   值有11个   因为从0数起   subcat[i][0]   ==   locationid屏蔽了再写     
  }     
  }     
  </script>     
    
  <form   name="form1"     method="post"   runat="server">     
  二级联动:     
    
  <select   name="s1"   onChange="changeselect1(this.value)">     
  <option>==请选择==</option>     
  <option   value="中文">中文</option>     
  <option   value="英语">英语</option> 
  <option   value="英语">法语</option> 
  </select>       
    
  <select   name="s2">     
  <option>==请选择==</option>     
  </select>     
  </form> 
<!-- by sundful  ending-->  
 </BODY>
</HTML>

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