Nth-child css property is counting html elements with display property set to none. How to change it?

Question

I have simple gallery using unordered list.

    <h1>Projects</h1>
    <hr>

    <!-- Projects gallery as unordered list -->

    <ul class="gallery">

      <li class="item residential">
        <img src="Projects/01-HighTorEast-EarlShilton/01-thumbnail.jpg" width="212" height="119" alt="High Tor East, Earl Shilton">
        <h2><a class="info" href="Projects/01-HighTorEast-EarlShilton/info.php">High Tor East, Earl Shilton</a></h2>
        <h3><a class="cat" href="residential">Residential</a></h3>
      </li>

      <li class="item modernisation">
        <img src="Projects/02-Hollycroft-Hinckley/02-thumbnail.jpg" width="212" height="119" alt="Hollycroft, Hinckley">
        <h2><a class="info" href="Projects/02-Hollycroft-Hinckley/info.php">Hollycroft, Hinckley</a></h2>
        <h3><a class="cat" href="modernisation">Modernisation & Domestic Extensions</a></h3>
      </li>

      <li class="item residential">
        <img src="Projects/03-SpaLane-Hinckley/03-thumbnail.jpg" width="212" height="119" alt="Spa Lane, Hinckley">
        <h2><a class="info" href="Projects/03-SpaLane-Hinckley/info.php">Spa Lane, Hinckley</a></h2>
        <h3><a class="cat" href="residential">Residential</a></h3>
      </li>

      <li class="item residential">
        <img src="Projects/04-Farnhambridge-Rothley/04-thumbnail.jpg" width="212" height="119" alt="Farnhambridge Farm, Rothley">
        <h2><a class="info" href="Projects/04-Farnhambridge-Rothley/info.php">Farnhambridge Farm, Rothley</a></h2>
        <h3><a class="cat" href="residential">Residential</a></h3>
      </li>

      <li class="item modernisation">
        <img src="Projects/05-NetherfieldClose-BroughtanAstley/05-thumbnail.jpg" width="212" height="119" alt="Netherfield Close, Broughtan Astley">
        <h2><a class="info" href="Projects/05-NetherfieldClose-BroughtanAstley/info.php">Netherfield Close, Broughtan Astley</a></h2>
        <h3><a class="cat" href="modernisation">Modernisation & Domestic Extensions</a></h3>
      </li>

      <li class="item modernisation">
        <img src="Projects/06-Bridlepath-Elmesthorpe/06-thumbnail.jpg" width="212" height="119" alt="Bridlepath, Elmesthorpe">
        <h2><a class="info" href="Projects/06-Bridlepath-Elmesthorpe/info.php">Bridlepath, Elmesthorpe</a></h2>
        <h3><a class="cat" href="modernisation">Modernisation & Domestic Extensions</a></h3>
      </li>

      <li class="item residential">
        <img src="Projects/07-Bridlepath-Elmesthorpe/07-thumbnail.jpg" width="212" height="119" alt="Bridlepath, Elmesthorpe">
        <h2><a class="info" href="Projects/07-Bridlepath-Elmesthorpe/info.php">Bridlepath, Elmesthorpe</a></h2>
        <h3><a class="cat" href="residential">Residential</a></h3>
      </li>

      <li class="item feasibility">
        <img src="Projects/08-GrangeCroft-Ullesthorpe/08-thumbnail.jpg" width="212" height="119" alt="Grange Croft, Ullesthorpe">
        <h2><a class="info" href="Projects/08-GrangeCroft-Ullesthorpe/info.php">Grange Croft, Ullesthorpe</a></h2>
        <h3><a class="cat" href="feasibility">Feasibility layouts</a></h3>
      </li>

      <li class="item master">
        <img src="Projects/09-RailwayInn-Sileby/09-thumbnail.jpg" width="212" height="119" alt="The Railway Inn, Sileby">
        <h2><a class="info" href="Projects/09-RailwayInn-Sileby/info.php">The Railway Inn, Sileby</a></h2>
        <h3><a class="cat" href="master">Master planning</a></h3>
      </li>


    </ul>

  </section>

than in my css I set right margin value to zero for every four child of .item class. I did that to keep four items in one row on my page and without removing margin I could only fit three.

ul.gallery { clear:both; list-style:none; margin:0; padding:0; width:940px; }
.gallery a:hover { text-decoration:underline; }
li.item { display:inline; margin:30px 20px 30px 0px; padding:0px; height:178px; width:220px; float:left; background:#ededed url('../Images/featuredline.png') repeat-x 0% 100%; overflow:hidden; }
li.item:nth-child(4n+4) { margin:30px 0px 30px 0px; }

Next, I've written small jQuery code to sort items by the category. So if someone clicks on 'residential' link it will hide elements with different categories.

    $('.cat').bind('click', function(e) {
    var cat = $(this).attr('href');
    $('.item').each(function () {
    var itemClass = $(this).attr('class');
    if (itemClass != 'item '+cat) {
        $(this).css({"display":"none"});
    };


    });
    e.preventDefault();

My problem is : when I sort my gallery items with above jQuery script it seems that .item:nth-child property is still counting elements which have display property set to none. I have no idea how to bite it. I need the css .item:nth-child property to count only visible elements after jQuery plugin fired.

website is available here http://www.damianwojtczak.com/avd2/projects.php

Answer 1

Remove your nth-child CSS style and every time you change the layout, call this:

$("li.item:visible").each(function(i) {
    if((i+1)%4==0) $(this).css("margin","30px 0");
    else $(this).css("margin","30px 20px 30px 0");
})

Just tested it on your site with firebug and worked a treat.

Answer 2

One solution is to change the nth-child css selector to a class and use jQuery to toggle the class.

li.item.marginClass { margin:30px 0px 30px 0px; }

JS:

$(function(){
    var $items=$('li.item');
    function toggleMargin(}{
        $items.removeClass('marginClass').filter(':visible').addClass(function(index){
              return index % 4 ===0 && index !=0 ? 'marginClass' : '';
        });
    }
    /* call for page loaded items*/
    toggleMargin(};

    $('.cat').bind('click', function (e) {
        /* filtering code here*/

        /* adjust class*/
         toggleMargin(};

    })



});