title: JQuery.append() after ajax success is not triggered
body: <p>My mind is blowing up looking for the reason and the solution of my problem. I know I miss something but I have no idea where it is. My objective is having an ajax call after the drop down is changed, then append option in select multiple. </p>
  
  <p>Here is what I have:</p>
  
  <pre><code>$(document).ready( function(){
      $('#myselect').append("&lt;option value='test1' selected&gt;Test1&lt;/option&gt;"); //this works
  
      $("#mydropdown").on('change', function(){
          $.ajax({
              type: "POST",
              url: "somepage.php",
              data: $("#someForm").serialize(),
              success: function(msg)
              {   
                  alert("Hello World"); //this is triggered
                  //below line of code does not work
                  $('#myselect').append("&lt;option value='test3' selected&gt;Tes3&lt;/option&gt;");
              }
          });
      });
  });
  </code></pre>
  
  <p>Why is this happening?</p>