三级联下拉

<script language="JavaScript" type="text/javascript">

 var bigtype=[
     ["咨询","病历","会诊","转诊","..."],
     ["高血压","心脏病","脑卒中","..."],
     ];
 var twotype=[
    ["专项档案","随访记录","用药记录","...."],
     ];
     function getOne(){
         //获得一类型下拉框的对象--门诊,慢病....
         var sltseltype=document.form1.seltype;
        
         //获得第一个子类下拉框的对象
         var sltseltype_two=document.form1.seltype_two;
        
         //得到对应一子类数组
         var selbigtype=bigtype[sltseltype.selectedIndex - 1];
        
         //清空第一子类，仅留提示选项
         sltseltype_two.length=1;
   
         //将第一个子类数组中的值填充到第一个子类下拉框中
         for(var i=0;i<selbigtype></selbigtype>
             sltseltype_two[i+1]=new Option(selbigtype[i],selbigtype[i]);
         }
         //如果选择门诊,则清空第三个列表里的值.回到最初状态.
         if(document.all.seltype.value=="mz")
         {
          document.form1.seltype_three.length=1;
         }
      }
     
      function getTwo()
      {
        if(document.all.seltype.value=="mz")
         {
          document.form1.seltype_three.length=1;
         }
         else
         {
         //获得第二类型下拉框的对象
          var sltseltype_twos=document.form1.seltype_two;
         
          //获得第三个子类下拉框的对象
          var sltseltype_three=document.form1.seltype_three;
         
          //得到对应第二个子类数组
          var seltwotype=twotype[sltseltype_twos.selectedIndex - 1];
         
          //清空第三个子类，仅留提示选项
          sltseltype_three.length=1;
 
          //将第二个子类数组中的值填充到第三个子类下拉框中
          for(var j=0;j<seltwotype></seltwotype>
              sltseltype_three[j+1]=new Option(seltwotype[j],seltwotype[j]);
          }
         }
       
      }

 </script>