CODE EXAMPLE FOR JAVASCRIPT

Swap a select text with javascript

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
<select id="se1">
  <option value="1">DOG</option>
  <option value="2">CAT</option>
  <option value="3">BIRD</option>
</select>
<button onclick="swap()">SWAP</button>
<select id="se2">
  <option value="4">DOG</option>
  <option value="5">CAT</option>
  <option value="6">BIRD</option>
</select>