<html>
<script src="https://code.jquery.com/jquery-2.2.4.js"></script>
<link href="https://rawgit.com/select2/select2/master/dist/css/select2.min.css" rel="stylesheet" />
<script src="https://rawgit.com/select2/select2/master/dist/js/select2.js"></script>
<select id="example" style="width: 300px">
<option></option>
<option value="JAN">January</option>
<option value="FEB">February</option>
<option value="MAR">March</option>
<option value="APR">April</option>
<option value="MAY">May</option>
<option value="JUN">June</option>
<option value="JUL">July</option>
<option value="AUG">August</option>
<option value="SEP">September</option>
<option value="OCT">October</option>
<option value="NOV">November</option>
<option value="DEC">December</option>
</select>
<script>
window.onpageshow = function() {
$('#example').select2({
allowClear: true,
placeholder: 'Select a month'
});
};
</script>
</html>