Change value of a select list using onclick in href

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

<a href="#" onClick="document.getElementById('action').value='a'">Add</a> 
<a href="#" onClick="document.getElementById('action').value='b'">Delete</a>