JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://code.jquery.com/jquery-3.2.1.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.js"></script>

<select id="selecter" multiple='multiple' size='6'>
  <option value="1">user1</option>
  <option value="2">user2</option>
  <option value="3">user3</option>
  <option value="3">user4</option>
  <option value="3">user5</option>
  <option value="3">user6</option>
</select>

JavaScript

$('#selecter option').click(function(){
    $(this).attr('selected', 'selected');
    //$(this).attr('selected', 'true');
    //$(this).prop('selected', 'selected');
    //$(this).prop('selected', 'true');
  });