$('.leave_response').on('change', function() {_x000D_
var responseId = $(this).val();_x000D_
console.log(responseId);_x000D_
});
_x000D_
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>_x000D_
<td>_x000D_
<select class="leave_response" name="leave">_x000D_
<option>1</option>_x000D_
<option>2</option>_x000D_
<option>3</option>_x000D_
<option>4</option>_x000D_
</select>_x000D_
</td>
_x000D_