Ajax dependable drop down list issue in Internet Explorer

Question

I have two drop down list in my webpage and one is dependent on the other. The Ajax code i am using is working fine in Chrome, Mozilla but not in IE (i am using IE9). Can someone please help me in getting this corrected.

This is the Ajax code-

 <script language="javascript" type="text/javascript">  
  var xmlHttp  
  var xmlHttp

  function showSubCategory(str){
      if (typeof XMLHttpRequest != "undefined"){
      xmlHttp= new XMLHttpRequest();
      }
      else if (window.ActiveXObject){
      xmlHttp= new ActiveXObject("Microsoft.XMLHTTP");
      }
      if (xmlHttp==null){
      alert("Browser does not support XMLHTTP Request")
      return;
      } 
      var url="jsp/subcategory.jsp";
      url +="?count=" +str;
      xmlHttp.onreadystatechange = stateChange1;
      xmlHttp.open("GET", url, true);
      xmlHttp.send(null);
      }

      function stateChange1(){   
      if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete"){   
      document.getElementById("subcat").innerHTML=xmlHttp.responseText   
      }   
      } 

This the main jsp page where the drop down lists are.--

 <table>
     <tr>
<td align="right" width="10%">Category </td>
<td>
   <select id='category' name="adv.categoryNo" onchange="showSubCategory(this.value)">  
       <option >Select the Category</option>  
     <%
Class.forName("com.mysql.jdbc.Driver").newInstance();  
Connection con1 = DriverManager.getConnection("jdbc:mysql://localhost:3306/db","user","pwd");  
Statement stmt1 = con1.createStatement();  
ResultSet rs1 = stmt1.executeQuery("Select * from categories");
while(rs1.next()){
    %>
    <option value="<%=rs1.getString(2)%>"><%=rs1.getString(2)%></option>  
    <%
}
    %>
    </select>                                  
     </td>
    </tr>

   Second drop down list 


    <tr>
      <td align="right" width="10%">Subcategory <span class="mandatory">*</span>: </td>
       <td>
         <div id='subcategory'>  
         <select id='subcat'  name='subcategory'>  
         <option >Select the Subcategory</option>  
         </select>  
         </div>
    </td>
    </tr>

Here is the subcategory jsp file which is called by Ajax.

<%@page import="java.sql.*"%>
 <%
  String category=request.getParameter("count");  
   String buffer="<select name='adv.subCategoryNo'><option >Select the Subcategory</option>";  
 try{
  Class.forName("com.mysql.jdbc.Driver").newInstance();  
  Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/db","user","pwd");  
  Statement stmt = con.createStatement();  
  ResultSet rs = stmt.executeQuery("Select * from subcategories where     categoryName='"+category+"' ");  
   while(rs.next()){
   buffer=buffer+"<option value='"+rs.getString(3)+"'>"+rs.getString(3)+"</option>";  
   }  
    buffer=buffer+"</select>";  
    response.getWriter().println(buffer); 
    }
   catch(Exception e){
    System.out.println(e);
    }
   %>

Strange thing is if i change the getElementById param in the following function of the Ajax code from " subcat " to " subcategory " which is the div id covering the second drop down list, it works fine in IE and other browsers.

function stateChange1(){   
      if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete"){   
      document.getElementById("subcat").innerHTML=xmlHttp.responseText   
      } 

If i follow the above approach i am not able to do any javascript form validation for that Subcategory select box using the following JS code.

 function madeSelectionCity(){
  var subcat = document.getElementById('subcat');
if(subcat.value == "Select the City name"){
    alert("Please select a subcategory first");
    subcat.focus();
    return false;
}else{
    return true;
}
 }

Hope i am clear in my question. Please let me know if any more explanation is required. Thanks

Answer 1

Change the below line of code( in subcategory.jsp called by ajax code)

 String buffer="<select name='adv.subCategoryNo'><option >Select the Subcategory</option>";  

to

 String buffer="<select id='subcat' name='adv.subCategoryNo'><option >Select the Subcategory</option>";  

and also add this line of code ( in subcategory.jsp called by ajax code)

response.setContentType("text/html");

on the webpage(main page) , the html should be

 <div id='subcategory'>
 </div>

and ajax(main page) code should be

function stateChange1(){   
      if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete"){   
      document.getElementById("subcategory").innerHTML=xmlHttp.responseText   
      }