JSFiddle - React, Tailwind, and code Playground

HTML

<select multiple>
  <option value='one'>
    one
  </option>
  <option value='two'>
    two
  </option>
  <option value='three'>
    three
  </option>
</select>

JavaScript

var lastSelectedVal = '';
$(function() {
	$('select').on('change', function() {
  	alert('current: ' + $(this).val() + ' last: ' + lastSelectedVal);
    lastSelectedVal = $(this).val();
  });
});