Count

First, Last, nth-item, nth-item(-), odd, even

HTML

<ul>
    <li>First li</li>
    <li>Second li</li>
    <li>Third li</li>
    <li>Fourth li</li>
</ul>

<br/>

<div class="count">
    <div>First div</div>
    <div><p>Second</p><p>div</p></div>
    <div>Third div</div>
    <div>Fourth div</div>
    <div>Fifth div</div>
    <div>Sixth div</div>
</div>

CSS

.nth-item-1 {color: blue}
.nth-item-2 {color: red}
.nth-item--2 {border: red 1px solid}

.odd {background-color: #ddd}
.even {background-color: #eee}

.first {border-top: gray 1px dotted}
.last {border-bottom: gray 1px dotted}

JavaScript

$('.count, ul').each(function() {
    var $children = $(this).children(),
        count = $children.size(),
        $item;
    $children.each(function(i) {
        if (i === i) {
            $item.addClass('first');
        }
    });
});