JSFiddle - React, Tailwind, and code Playground

HTML

<select id="">
    <option value="add" selected="selected">Add</option>
    <option value="edit">Edit</option>
    <option value="delete">Delete</option>
</select>
<a class="button add" style="cursor:pointer;"><span><b>Add Purchase Request</b></span></a>
 <a class="button edit" style="cursor:pointer;"><span><b>Edit Purchase Request</b></span></a>
 <a class="button remove" style="cursor:pointer;" name="remove"><span><b>Remove Purchase Request</b></span></a>

JavaScript

$('select').change(function () {
    var index = $(this).find('option:selected').index();
    $('a.button').eq(index).show().siblings('a').hide();
}).change();