JAVASCRIPT

select2 clear options

Remove the selected options : 
-----------------------------
$('#mySelect2').val(null).trigger('change');

============================================

Completly remove the select2 initialization :
--------------------------------------------
$('#payment_method').html('').select2({data: [{id: '', text: ''}]});

select2 clear selected

$("#mySelect2").select2({
    allowClear: true
});

select2 clear fields

$('#mySelect2').val(null).trigger('change');