JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://github.com/ehynds/jquery-ui-multiselect-widget/raw/master/src/jquery.multiselect.min.js"></script>
<link rel="stylesheet" href="http://github.com/ehynds/jquery-ui-multiselect-widget/raw/master/jquery.multiselect.css">
<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.5/themes/base/jquery-ui.css">
    <select id="theme" name="theme" multiple="multiple" size="5" style="width:220px">
<option value="foo">foo</option>
<option value="bar">bar</option>
<option value="baz">baz</option>
</select>

<p id="blaster">blaster</p>

CSS

#target { padding: 5px; border: 1px solid #000; width:200px; float:right }

JavaScript

var s = $("#theme").multiselect();
$("#blaster").click(function() {

    
    
  var array_of_checked_values = s.multiselect("getChecked").map(function(){
   return this.value;
}).get();


    alert( array_of_checked_values.join() );
    
    
});