Bootstrap Select Picker append add new item if search not exist

 <select class="selectpicker" data-live-search="true" id="branch" multiple>

        <option>B.Tech</option>
        <option>M.Tech</option>
        <option>Ph.D</option>
</select>

jQuery script

$('.selectpicker').selectpicker({
noneResultsText: 'No result found <button class="btn btn-dark" onclick=(add_opt(this))>Add new option</button>'
}); 

function add_opt(event){
var value = $(event).parents('div').siblings('.bs-searchbox').find('input').val();
$(event).parents('div').siblings('.selectpicker').append($("<option></option>").text(value)).val(value);
$('.selectpicker').selectpicker('refresh');
}