依赖下拉列表不起作用 - Dependent dropdown not working

在下面的代码中更新部分：有2个文本框和2个下拉框。一个下拉列表是课程代码，另一个是科目代码。当我通过选择课程代码更新科目代码时，相应的代码没有显示，它在科目代码下拉列表中显示空白屏幕。请任何人帮帮我。

     View:Student_detail_view

<section id="tables">
<script>
 jQuery(document).ready(function() {
  oTable = jQuery('#studenttable').dataTable({
   "bJQueryUI": true,
   "sPaginationType": "full_numbers"
  });
   }); 
  </script> 
  <script type="text/javascript" charset="utf-8">
 function get_studentdetails() {
    var exam_name = jQuery('#exam_name_id').val();
    //alert("exam_name"+exam_name);
    jQuery.ajax({
        data: {
            exam_name: exam_name,
        },
        type: 'POST',
        url: 'student_site/studentupdate',          
        success: function(data){
        //alert("inside change");
            console.log(data);
            jQuery('#details').html(data);
            jquery('#deleting').html(data);
        }
    });
    jQuery(document).ready(function(){
    jQuery.ajax({
        data: {
            exam_name: exam_name,
        },
        type: 'POST',
        url: 'student_site/studentcreate',
        success: function(data){
        //alert("inside change");
            console.log(data);
            jQuery('#crud').html(data);
            jquery('#deleting').html(data);
        }
    }); 
    });
}     
function CheckBoxVerification(From)
{
alert('hai');
    alert('hai:' $("table input[type=checkbox]:checked").length);
    if(From == "Insert")
    {
        if(!!$('#rowInsert input:checked').length == false)
        {
            alert('please select at least one check box to Create ...!');
        }
    }
    if(From == "Update")
    {
        if(!!$('#rowUpdate input:checked').length == false)
        {
            alert('please select at least one check box to Update ...!');
        }
    }
}
  function get_subjectdetails1() {
    //var index = jQuery('#index').val();
    var course_name = jQuery('#course_name_id').val();
    //alert("course_name"+course_name);
    var exam_name = jQuery('#course_name_id>option:selected').text();
    var exam_name = jQuery('#exam_name_id').val();
    var ssubject_code = jQuery('#ssubject_code_id').val();
    //var partsArray = exam_name.split('.');
    //alert("ssubject_code"+ssubject_code);
    //alert("course_name"+course_name);
    //alert("exam_name"+exam_name);
    jQuery.ajax({
        data: 'exam_name='+exam_name+'&course_name=' + course_name,
        type: 'POST',
        url: 'student_site/subject_records',
        success: function(data){
        //alert("inside change");
            console.log(data);
            //alert ("data"+data);
            //for(var j = course_name; j < ssubject_code; j++)
        //{
            jQuery('#ssubject_code').empty().append(data);
        //}
        }
    });
} 
</script>
<?php 
    $attributes=array(
        'name'=>'updatecustomer',
        'id'=>'updatecustomer'
        );
    echo form_open('student_site/manage_student',$attributes);
?>
<div id="validation_failed">
    <?php
        echo validation_errors();
    ?>
    <?php $data = array();
        foreach ($course_records as $row)
        {
            $data[$row->course_code] = $row->course_code; 
        } 
        $subject_data = array();
        foreach ($all_coursesubject_records as $row)
        {
            $subject_data[$row->subject_code] = $row->subject_code; 
        }  

     ?>
     <div id="Processy">
<table class="display table table-bordered table-striped" id='studenttable'>
<thead>
<tr font style='font-size:13px'>
<th>&nbsp;</th>
<th>&nbsp;</th>
<th>Register Number</th>
<th>Name </th>
<th>Course Code</th>
<th>Subject Code</th>
</tr></thead>
<?php if(isset($records)) : foreach($records as $row) : ?>
<tr >
<td>
<?php echo anchor('student_site/delete/'.$row->id, 'Delete',array('onClick'=>"return confirm('Are you sure want to delete..?')")); ?>
</td>
<td id="rowUpdate">
<input type=checkbox name="editstudent[]" id="editstudent[]" value="<?php echo $row->id ?>">
</td>
<td ><input class="inputmedium span2" type="text" name="register_number_<?php echo $row->id ?>" id="register_number_<?php echo $row->id ?>" value="<?php echo $row->register_number; ?>" ></td>
<td ><input class="inputmedium span2" type="text" name="name_<?php echo $row->id ?>" id="name_<?php echo $row->id ?>" value="<?php echo $row->name; ?>" ></td>
<td >
<?php 
        $js = 'class="dropdown_class" id="course_code_id'.$row->id.'" onChange="get_subjectdetails112('.$row->id.')" '; 
        $js_name = 'course_code_id'.$row->id;
        echo form_dropdown($js_name, $data, $row->course_code, $js);
?>
</td>
<td>    
<?php 

        $js = 'class="dropdown_class" id="subject_code_id'.$row->id.'"'; 
        $js_name = 'subject_code_id'.$row->id;
        echo form_dropdown($js_name, $subject_data, $row->subject_code, $js);
?>


</td>
</tr>
<?php endforeach; ?>
</table>
</div>
<center>
<br /><input type="submit" class="btn-success btn" value="Update Student"></center>
<?php else : ?>
<h2>No records were returned.</h2>
<?php endif; ?>


view:student_update:
<script type="text/javascript" charset="utf-8">
function enableDisable(bEnable, textBoxID1, textBoxID2, chkBox)
{
    document.getElementById(textBoxID1).disabled = !bEnable
    document.getElementById(textBoxID2).disabled = !bEnable
    document.getElementById(chkBox).disabled = !bEnable
}
</script>
<script type="text/javascript" charset="utf-8">
 function get_subjectdetails112(index) {
 alert ("enter first");
    //var index = jQuery('#index').val();
    //alert("index"+index);
    var course_name = jQuery('#course_code_id'+index).val();
    alert("course_name"+course_name);
    //var exam_name = jQuery('#course_name_id>option:selected').text();
    var exam_name = jQuery('#exam_name_id').val();
    var ssubject_code = jQuery('#subject_code_id'+index).val();
    //var partsArray = exam_name.split('.');
    //alert("ssubject_code"+ssubject_code);
    //alert("course_name"+course_name);
    //alert("exam_name"+exam_name);
    jQuery.ajax({
        data: 'exam_name='+exam_name+'&course_name=' + course_name,
        type: 'POST',
        url: 'student_site/subject_records',
        success: function(data){
        //alert("inside change");
            console.log(data);
            //alert ("data"+data);
            //for(var j = course_name; j < ssubject_code; j++)
        //{
            jQuery('#subject_code_id'+index).empty().append(data);
        //}
        }
    });
} 
 function get_subjectdetails1(index) {
 alert ("enter first");
    //var index = jQuery('#index').val();
    //alert("index"+index);
    var course_name = jQuery('#course_name_id'+index).val();
    alert("course_name"+course_name);
    //var exam_name = jQuery('#course_name_id>option:selected').text();
    var exam_name = jQuery('#exam_name_id').val();
    var ssubject_code = jQuery('#ssubject_code'+index).val();
    //var partsArray = exam_name.split('.');
    //alert("ssubject_code"+ssubject_code);
    //alert("course_name"+course_name);
    //alert("exam_name"+exam_name);
    jQuery.ajax({
        data: 'exam_name='+exam_name+'&course_name=' + course_name,
        type: 'POST',
        url: 'student_site/subject_records',
        success: function(data){
        //alert("inside change");
            console.log(data);
            //alert ("data"+data);
            //for(var j = course_name; j < ssubject_code; j++)
        //{
            jQuery('#ssubject_code'+index).empty().append(data);
        //}
        }
    });
} 
 function student_updatedetails() {
        var register_number = jQuery('#register_number').val();
        var exam_name = jQuery('#exam_name_id').val();
        var name = jQuery('#name').val();
        var course_code = jQuery('#course_name_id').val();
        var subject_code = jQuery('#subject_name_id').val();
        //alert("register_number"+register_number+"name"+name+"exam_name: "+exam_name+"course_code"+course_code+"subject_code:"+subject_code);
        jQuery.ajax({
        data: 'exam_name=' + exam_name + '&register_number=' + register_number + '&name=' + name + '&course_code=' + course_code + '&subject_code=' + subject_code,
        type: 'POST',
        url: 'student_site/update',
        success: function(data){
            console.log(data);
            jQuery('#details').html(data);
        }
    });
} 
function CheckBoxVerification(From)
{
//alert('hi');
    if(From == "Insert")
    {
        if(!!$('#rowInsert input:checked').length == false)
        {
            alert('please select at least one check box to Create ...!');
        }
    }
    if(From == "Update")
    {
        if(!!$('#rowUpdate input:checked').length == false)
        {
            alert('please select at least one check box to Update ...!');
        }
    }
}
</script>


<br>
<div class="page-header">
    <h1 class="colored"><small><a>Create Student</a></small></h1>
  </div><br />
  <div class="well">
  <?php 
@$rcount=3;
//echo "rcount:".$rcount;
echo form_open('student_site/create_student/'.$rcount); ?>
<table>
<?php
  $j=1; 
  while($j<=$rcount)
  {
 ?>
<tr id="rowInsert">
<td>
<input type=checkbox name="createstudent[]" id="createstudent[]" onclick="enableDisable(this.checked, 'register_number_<?php echo $j ?>','name_<?php echo $j ?>', 'course_name_id<?php echo $j ?>');" value="<?php echo $j ?>">
</td>
<td><input type="text" id="register_number_<?php echo $j ?>" name="register_number_<?php echo $j ?>" required placeholder="Register_Number" class="span2" disabled="true"/></td>
<td><input type="text" id="name_<?php echo $j ?>" name="name_<?php echo $j ?>" onblur="ucwords(this)" placeholder="Name" required class="span2" disabled="true"/></td>
<?php
$cnt=0;
?>
<td>
  <?php 
        $data = array(
        );
        $data["Select Course Code"] = "Select Course Code";
        foreach ($course_records as $row)
        {
            $data[$row->course_code] = $row->course_code; 
        } 
        //echo form_dropdown('course_name', $data, 'small', 'class="dropdown_class span2" id="course_name_id" onChange="get_subjectdetails()"');
        $js = 'class="dropdown_class" id="course_name_id'.$j.'" onChange="get_subjectdetails1('.$j.')" disabled="true"'; 
        $js_name = 'course_name_id'.$j;
        echo form_dropdown($js_name, $data, 'small', $js);      
?>
<input type="hidden" name="index" id="index" value="<?php echo $j; ?>"/>
</td>
<td>
<div id="ssubject_code<?php echo $j; ?>" ></div>
<input type="hidden" name="ssubject_code" id="ssubject_code" value="ssubject_code<?php echo $j; ?>"/>
</td>
<?php 
   $j++;
  }
?>
</tr>
</table>
<input type="hidden" name="exam_name" id="exam_name" value="<?php echo $exam_name; ?>"/>
<input type="submit" value="Create Student" class="btn-success btn" onclick="CheckBoxVerification('Insert')"id="start_button"/>

</div>
<?php echo form_close(); ?>


<br />
</center>

如果只有相关的代码，而不必试图弄清楚代码的哪一部分应该填充这些框，那就太好了。我怀疑这是因为你试图将值放入一个选择框中，而不是在数组中迭代并每个添加一个选项。这是我的一个应用程序中的一段代码，它清除了一个下拉列表，并用新值重新填充它。这些值以数组形式从服务器返回：AddressId=>address

You should be able to see the parts that you need and modify it to your uses.
function loadAddresses()
{
    $.ajax({
        type: "POST",
        url: "/aj_getAddresses/",
        data: { companyId: $('#companyId').val() },
        dataType: "json",
        success: function(data) {
            if(data.status=="success")
            {
                $("#addressId").find('option').remove();
                $.each(data.addresses, function(key, val) {
                    $("#addressId").append(
                        '<option value="' + key + '">' + val + '</option>'
                    );
                });
            } else {
                $("#error").html(data.message);
            }
        },
        error: function(error) {
        }
    });
}