JAVASCRIPT

f.select on change jquery

$('select').on('change', function() {
  alert( this.value );
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<select>
    <option value="1">One</option>
    <option value="2">Two</option>
</select>

jquery detect select change

Script/Jquery code
---------------------------------------------------
$('#selectChange').on('change', function() {
  alert( this.value );
});


HTML PART
---------------------------------------------------
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<select id="selectChange">
    <option value="1">One</option>
    <option value="2">Two</option>
</select>