select2 add select all option code example
Example: select2 add option
// 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');
}