请教js问题

<!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><script language="JavaScript">
    function funchange(str)
    {
      var strNote;
      var a = str.slice(0,-2);
      var b = str.slice(-1);
      strNote = '<INPUT TYPE="checkbox" NAME="zz" value="'+a+'">'+a+'<br><INPUT TYPE="checkbox" NAME="zz" value="'+b+'">'+b
      return strNote;
    }
    
    function show_info()
    {
         var sel = form1.select.options[form1.select.selectedIndex];
         //alert(sel.text);
         form1.action = "check.asp?add_type="+sel.value;
         //form1.test.value = sel.text;
         document.all.textEng.innerHTML = funchange(sel.engText);
    }
</script> 
</head>
<body>
    <span id="chg_action">
        <form name="form1" method="post" action="check.asp"></span>
            <SELECT NAME="select" size="1" onchange="show_info()">
                <option value="1" selected engText="a,b">micro</option>
                <option value="2" engText="c,d">Euml</option>
                <option value="3" engText="e,f">aelig</option>
                
            </SELECT>
<!--            <INPUT TYPE="text" NAME="test">-->
<div id="textEng" name="car_part"><INPUT TYPE="checkbox" NAME="zz" value="a">a<br><INPUT TYPE="checkbox" NAME="zz" value="b">b</div>
        </form>
   </span>
</BODY>
</HTML>