Manage last row items

Adjuting margin-bottom of last-row items that :last-of-type can't address.

HTML

<form class="last_row_management" data-item_selector="fieldset">
  <fieldset>
    <input type="text" value="one" />    
  </fieldset>
  <fieldset>
    <input type="checkbox" />two
  </fieldset>
  <fieldset>
    <input type="checkbox" />three
  </fieldset>
  <fieldset>
    <input type="button" value="four" />
  </fieldset>
  <fieldset>
    <input type="checkbox" />five
  </fieldset>
  <fieldset>
    <input type="text" value="six" />    
  </fieldset>
  <fieldset>
    <input type="button" value="seven" />
  </fieldset>
  <fieldset>
    <input type="button" value="eight" />
  </fieldset>
</form>

<div class="clear"></div>

<ul class="last_row_management" data-item_selector="li">
  <li>one</li>
  <li>two</li>
  <li>three</li>
  <li>four</li>
  <li>five</li>
  <li>six</li>
  <li>seven</li>
  <li>eight</li>
  <li>nine</li>
  <li>ten</li>
  <li>eleven</li>
  <li>twelve</li>
</ul>

CSS

/* ------------- necessary ------------------ */

.last_row_item {
background-color: turquoise;
	margin-bottom: 0 !important;
}


/* ------------- just for this fiddle ------------- */

body {
  font-family: 'Tahoma';
}

.clear {
  clear: both;
  border-bottom: 1px solid black;
}

fieldset {
  display: inline-block;
  float: left;
  height: 30px;
  margin-right: 20px;
  margin-bottom: 50px;
}

ul {
  list-style-type: none;
  margin: 40px 0 0;
  padding: 0;
}

li {
  width: 100px;
  height: 100px;
  float: left;
  margin-bottom: 50px;
  margin-right: 30px;
  border: 1px solid black;
}

JavaScript

// tries to adjust margin-bottom of last-row elements.
function manage_last_row_items(){

  $('.last_row_management').each(function(){
    var
      $context = $(this),
      item_selector = $context.data('item_selector'),
      $last_item = $context.find(item_selector +':last-of-type').addClass('last_row_item'),
      final_top = $last_item.offset()  ? $last_item.offset().top  : 0
    ;
    $context.find(item_selector)
      .not($last_item)
        .removeClass('last_row_item')
        .filter(function(){
          var
            o = $(this).offset(),
            decision = false
          ;
          if (o) {
            decision = o.top === final_top;
          }

          return decision;
        })
          .addClass('last_row_item')
    ;
  });  // end of ( each )
}



$(document).ready(function(){
  manage_last_row_items();
  $(window).resize(manage_last_row_items);
});