jQuery on（change）第二次不起作用

Question

I have cascading dropdown menus as below. I am listing selections dynamically on second and third dropdowns. While the first on change function works without problem (i am getting project list), the second on change ( $("#pro").on('change', function(e) ) simply doesn't sense any change on selection of projects. Chrome console shows no problem. What can be the problem?

<div class="form-group">
  <label for="projectfamily">Proje Grubu</label>
  <select class="form-control" name="projectfamily" id="projectfam">
    <option value="">Seçiniz</option>
    @foreach($projectfamilies as $projectfamily)
    <option value= "{{$projectfamily->id}}">{{$projectfamily->projectfamily}}</option>
    @endforeach
  </select>
</div>

<div class="form-group">
  <label for="project">Proje Adı</label>
  <select class="form-control" name="project" id="pro">
    <option value= "" disabled></option>
  </select>
</div>

<div class="form-group">
  <label for="version">Versiyon</label>
  <select class="form-control" name="version" id="version">
    <option value="" disabled></option>
  </select>
</div>

JQuery

$('#projectfam').on('change', function(e) {
    var projectfam = e.target.value;
    $.get('/ajax_projectfamily_post?projectfam=' + projectfam, function(data){
        $('#pro').empty();
        $('#version').empty();  
        $('#pro').append('<option value="' + '">' + "Seçiniz" + '</option>');

        $.each(data, function(i, deger){
            $('#pro').append('<option value="' + deger.id + '">' + deger.project + '</option>');
        });
    });
});

$("#pro").on('change', function(e) {
    var project = e.target.value;
    $.get('/ajax_project_post?project=' + project, function(data){
        $('#version').empty();
        $('#version').append('<option value="' + '">' + "Seçiniz" + '</option>'); 
        $.each(data, function(i, deger) {
            $('#version').append('<option value="' + deger.id + '">' + deger.version + '</option>');
        });
    });
});

Answer 1

It appears to work as expected in chrome. See this fiddle with the ajax calls replaced. Is it a problem with the ajax call? Or perhaps an html syntax error? Check the validity of your entire HTML page. Since you only posted a fragment I can't diagnose further.

$('#projectfam').on('change', function(e) {
    var projectfam = e.target.value;
    var data = ['a', 'b', 'c'];

    $('#pro').empty();
    $('#version').empty();  
    $('#pro').append('<option value="' + '">' + "Seçiniz" + '</option>');

    $.each(data, function(i, deger){
        $('#pro').append('<option value="' + data[i] + '">' + data[i] + '</option>');
    });
});

$("#pro").on('change', function(e) {
    var project = e.target.value;
    var data = ['x', 'y', 'z'];
    $('#version').empty();
    $('#version').append('<option value="' + '">' + "Seçiniz" + '</option>'); 
    $.each(data, function(i, deger) {
        $('#version').append('<option value="' + data[i] + '">' + data[i] + '</option>');
    });
});

Answer 2

I would do it like this, I had a similar problem before, the onchange events need to be assigned after the elements are loaded:

$('#projectfam').on('change', function(e) {
    var projectfam = e.target.value;
    $.get('/ajax_projectfamily_post?projectfam=' + projectfam, function(data){
        $('#pro').empty();
        $('#version').empty();  
        $('#pro').append('<option value="' + '">' + "Seçiniz" + '</option>');

       $.each(data, function(i, deger){
            $('#pro').append('<option value="' + deger.id + '">' + deger.project + '</option>');
       });
       addOnChangeThingy(); // load onclick functions
   });
});

function addOnChangeThingy(){
   $("#pro").on('change', function(e) {
      var project = e.target.value;
      $.get('/ajax_project_post?project=' + project, function(data){
          $('#version').empty();
          $('#version').append('<option value="' + '">' + "Seçiniz" + '</option>'); 
          $.each(data, function(i, deger) {
             $('#version').append('<option value="' + deger.id + '">' + deger.version + '</option>');
           });
       });
   });
 }