How to set selected value of jQuery Select2

Question

This belong to codes prior to Select2 version 4

I have a simple code of select2 that get data from AJAX.

$("#programid").select2({
  placeholder: "Select a Program",
  allowClear: true,
  minimumInputLength: 3,
  ajax: {
    url: "ajax.php",
    dataType: 'json',
    quietMillis: 200,
    data: function (term, page) {
      return {
        term: term, //search term
        flag: 'selectprogram',
        page: page // page number
      };
    },
    results: function (data) {
      return {results: data};
    }
  },
  dropdownCssClass: "bigdrop",
  escapeMarkup: function (m) { return m; }
});

This code is working, however, I need to set a value on it as if in edit mode. When user select a value first time, it will be saved and when he needs to edit that value it must appear in the same select menu (select2) to select the value previously selected but I can't find a way.

UPDATE:

The HTML code:

<input type="hidden" name="programid" id="programid" class="width-500 validate[required]">

Select2 programmatic access does not work with this.

Answer 1

The third parameter of the new Option (...) determines if the item is "selected by default". That is, it sets the selected attributes of the new option. The fourth parameter sets the currently selected status of the option. If set to true, the new option will be selected by default.

Create if it does not exist 
You can use .find to select an option if it already exists, otherwise you can create it.

// Set the value, creating a new option if necessary
if ($('#mySelect2').find("option[value='" + data.id + "']").length) {
    $('#mySelect2').val(data.id).trigger('change');
} else { 
    // Create a DOM Option and pre-select by default
    var newOption = new Option(data.text, data.id, true, true);
    // Append it to the select
    $('#mySelect2').append(newOption).trigger('change');
}