Dynamically add item to jQuery Select2 control that uses AJAX

Question

I have a jQuery Select2 control that uses AJAX to populate:

<input type="text" name="select2" id="select2" style='width:400px' value="999">

var initialSelection = { id: '999', text:"Some initial option"};

$("#select2").select2({
    placeholder: "Select Option",
    minimumInputLength: 2,
    ajax: { 
        url: "/servletToGetMyData",
        dataType: 'json',
        data: function (term, page) { return { term: term }; },
        results: function (data, page) {  return { results: data.results} }
    },
    initSelection : function(element, callback){ callback(initialSelection); },     
    escapeMarkup: function (m) { return m; }
}); 

The AJAX links to a database of possible options and as you can see requires two characters of input.

The problem is the user can use a dialog to add a new option if the option doesn't exist in the database. Upon return from that dialog, I try:

var o = $("<option/>", {value: newID, text: newText});
$('#select2').append(o);
$('#select2 option[value="' + newID + '"]').prop('selected',true);
$('#select2').trigger('change');

But it doesn't work. The same exact code works for non-AJAX Select2 boxes. I've tried various alternatives, like using $('#select2').select2("val", newID); but it doesn't work.

I've even tried completely deleting the Select2 control. However, $('#select2').remove() only removes the original <input> field but leaves the Select2 control lingering around. Note that the page has more than one Select2 control, so I can't use a class selector for Select2 controls as it will remove other controls that I need.

Any idea how to either a) dynamically add an option to a Select2 control that uses AJAX; or b) completely delete a Select2 control so that it can be programmatically added back? Or any other solution...

Edit I found another question that shows how to remove a select2 element, using .select2("destroy"). This works but is, in my opinion, sub-optimal. I would much prefer to be able to just add the option than to destroy and re-create the select2.

Answer 1

This is a lot easier to do starting in select2 v4. You can create a new Option, and append it to the select element directly. See my codepen or the example below:

$(document).ready(function() {
    $("#state").select2({
      tags: true
    });
      
    $("#btn-add-state").on("click", function(){
      var newStateVal = $("#new-state").val();
      // Set the value, creating a new option if necessary
      if ($("#state").find("option[value=" + newStateVal + "]").length) {
        $("#state").val(newStateVal).trigger("change");
      } else { 
        // Create the DOM option that is pre-selected by default
        var newState = new Option(newStateVal, newStateVal, true, true);
        // Append it to the select
        $("#state").append(newState).trigger('change');
      } 
    });  
});

<link href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.6/css/bootstrap.min.css" rel="stylesheet"/>
<link href="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.1/css/select2.min.css" rel="stylesheet"/>

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.6/js/bootstrap.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.1/js/select2.min.js"></script>


<select id="state" class="js-example-basic-single" type="text" style="width:90%">
  <option value="AL">Alabama</option>
  <option value="WY">Wyoming</option>
</select>
<br>
<br>
<input id="new-state" type="text" />
<button type="button" id="btn-add-state">Set state value</button>

Hint: try entering existing values into the text box, like "AL" or "WY". Then try adding some new values.