How to get the value of the checked boxes in jquery

I have a following code in html, which use checkbox align as a row

<tr class="reg_name">
  <th class="custom-th">Reg. Name</th>
  <td class="text-center"><input type="checkbox" name="reg_name[]" value="Y:1"></td>
  <td class="text-center"><input type="checkbox" name="reg_name[]" value="N:1"></td>
  <td class="text-center"><input type="checkbox" name="reg_name[]" value="B:1"></td>
  <td class="text-center"><input type="checkbox" name="reg_name[]" value="I:1"></td>
</tr>

with a button

<button type="button" class="purchase__save btn btn-default pull-right">Save</button>

and this js code,

$(document).ready(function() {
  $('.purchase__save').click(function() {
    var box_array = [];
    var boxes = $('.reg_name input[name="reg_name[]"]:checked');
    for (var i = 0; i < boxes.length; i++) {
      box_array[i] = boxes.val();
    }
    console.log(box_array);
  });
});

will try to get the value of checked box.

The problem, if try to check two checkboxes at the same time, the value from this <td class="text-center"><input type="checkbox" name="reg_name[0]" value="Y:1"></td> is the only thing I get.

How to get values of other checkboxes if they are checked?