JSFiddle - React, Tailwind, and code Playground

HTML

<form>
      <select id="action">
         <option value="a">Add</option>
         <option value="b">Delete</option>
      </select>
 </form>

<a href="#" onClick="changeval()">Add</a> 
<a href="#" onClick="changeval()">Delete</a>

JavaScript

function changeval()
{

if(document.getElementById('action').value =='b')
document.getElementById('action').value='a'
else
document.getElementById('action').value='b'

}