Answers for "clear the options on select"

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 select clear options

$('#mySelect')
    .find('option')
    .remove()
    .end()
    .append('<option value="whatever">text</option>')
    .val('whatever')
;