JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://silviomoreto.github.io/bootstrap-select/bootstrap-select.min.css">
<script src="http://silviomoreto.github.io/bootstrap-select/bootstrap-select.min.js"></script>
 <select class="selectpicker" multiple title="Not changable text" data-count-selected-text="Not changable text" data-selected-text-format="count>0">
         <option>Mustard</option>
         <option>Ketchup</option>
         <option>Relish</option>
 </select>

<button id="f1">ggg</button>

JavaScript

$('#f1').click(function(){

   var rr = []; 
$('.selectpicker :selected').each(function(i, selected){ 
  rr[i] = $(selected).text(); 
});
    alert(rr);
});