Answers for "set value select 2"

select2 clear options

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

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

jquery to set value in select2 dropdown button

$("#u20_cre").select2().val(["1","6"]).trigger("change");