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Editorial Team
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Asked: 2026-05-29T12:16:28+00:00

I populate child dropdown (second dropdown) by the onchange event in parent dropdown (first

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I populate child dropdown (second dropdown) by the onchange event in parent dropdown (first dropdown). After that by onchange event of child dropdown I am autofilling three text boxes. But my issue is with first dropdown. Id of first dropdown is combo and id of second dropdown is combo1.

When I select A from first dropdown then I in second dropdown I have got a value 1 by appending in javascript written below in auto.jsp. But when I select option B in first dropdown then I got 2 in second dropdown but the old value 1 should be removed from second dropdown, but it is still remaining there, why? Similarly when I am selecting A or B from first dropdown multiple times then multiple values 1 or 2 are coming in second dropdown which I want to remove and to display single times that is if A will be selected then 1 will be displayed and if B will be selected then 2 will be displayed, how can it be done?

auto.jsp

   <script type="text/javascript">
  $(document).ready(function() {
 $("#combo").change(function() {// by onchange event in first dropdown I populate  second dropdown having id combo1
  $.getJSON('combo1.jsp', {firstcombobox : this.value}, function(responseData) {
   $("#combo1").append(
$("<option></option>").html(responseData.name).val(responseData.name)
);
  });
});
// After getting value in second dropdown, by onchange event i am autofilling 3 textboxes.
$("#combo1").change(function() {

 $.getJSON('combo2.jsp', { combo1Val : $(this).val() }, function(data) {

 $("#firsttextbox").val(data.name);
$("#secondtextbox").val(data.roll_no);
 $("#thirdtextbox").val(data.fine);
  });
 });
});          
    </script>
<body>
//First dropdown
 <select id="combo" name="firstcombobox">

     <option value="">select</option>
      <option value="a">A</option>
       <option value="b">B</option>
        </select> 
// Second dropdown
      <select id="combo1" name="combo1Val" >
     <option value="">select</option>
 </select> 
</body>

combo1.jsp

<%@page import="net.sf.json.JSONObject"%>
<%@page import="net.sf.json.JSONArray"%>
<%
String firstcombobox=request.getParameter("firstcombobox");

if(firstcombobox.equalsIgnoreCase("a")){// If selected value in first dropdown is A then 1 will be displayed as written below
JSONObject arrayObj= new JSONObject();

       arrayObj.put("name","1");// I displayed 1 in second dropdown option when A is selected
          response.setContentType("application/json");
      response.getWriter().write(arrayObj.toString());
      }
else if(firstcombobox.equalsIgnoreCase("b")){
  JSONObject arrayObj= new JSONObject();
       arrayObj.put("name","2");
          response.setContentType("application/json");
      response.getWriter().write(arrayObj.toString());
}
else{
}
%>
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1 Answer

  1. Editorial Team

    In auto.jsp ‘#combo’ change anonymous function, replace:

    $.getJSON('combo1.jsp', {firstcombobox : this.value}, function(responseData) {
    $("#combo1").append(
        $("<option></option>").html(responseData.name).val(responseData.name)
    );
});

    with:

    $.getJSON('combo1.jsp', {firstcombobox : this.value}, function(responseData) {
    $("#combo1").empty().append(
        $("<option></option>").html(responseData.name).val(responseData.name)
    );
});

    To split the string into an array look here: How do I split a string, breaking at a particular character?

    They use as follows:

    $.getJSON('combo1.jsp', {firstcombobox : this.value}, function(responseData) {
    var splitValues = responseData.name.split(/,/);

    $("#combo1").empty().append("<option value="0">Please select...</option>");

    for (var idx in splitValues) {
        $("#combo1").append(
            $("<option></option>").html(splitValues[idx]).val(splitValues[idx])
        );
    }
});

    Hope this helps?

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