JQUERY: Check/Uncheck with single button

JQUERY: Check & Uncheck with single button

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<SCRIPT language="javascript">
$(document).ready(function() {
  $("#parent").click(function() { 
  	var d = $(this).data(); 
    $(".child").prop("checked", !d.checked);
   // $('#parentnone').prop('checked', false);   
    //d.checked = !d.checked;
  });

  $("#parentnone").click(function() {
  	var d = $(this).data(); 
  	$('#parent').prop('checked', d.checked);   
  	$(".child").prop("checked", false);
  });

  $('.child').click(function() {
    if ($('.child:checked').length == $('.child').length) {
      $('#parent').prop('checked', true);
    } else {
      $('#parent').prop('checked', false);
    }
  });
});

</SCRIPT>
 <button id="parent" data-checked='false' style="background-color: transparent;border: none;">All</button> <br/>
<button id="parentnone" data-checked='false' style="background-color: transparent;border: none;">None</button> <br/> 

<hr/>

<ul>
  <li>
    <input type="checkbox" class="child" /> Checkbox 1</li>
  <li>
    <input type="checkbox" class="child" /> Checkbox 2</li>
  <li>
    <input type="checkbox" class="child" /> Checkbox 3</li>
</ul>