Adding class to every third element

by labanino

HTML

<div class="content">
    <div class="box">
        <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec convallis lorem id tortor rutrum, nec tincidunt nisi consequat. Phasellus dictum leo eu enim placerat convallis. Praesent quis est id ipsum tempor euismod sed sit amet massa.</p>
    </div>
    <div class="box">
        <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec convallis lorem id tortor rutrum, nec tincidunt nisi consequat. Phasellus dictum leo eu enim placerat convallis. Praesent quis est id ipsum tempor euismod sed sit amet massa.</p>
    </div>
    <div class="box">
        <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec convallis lorem id tortor rutrum, nec tincidunt nisi consequat. Phasellus dictum leo eu enim placerat convallis. Praesent quis est id ipsum tempor euismod sed sit amet massa.</p>
    </div>
</div>

CSS

.box {
    float: left;
    width: 25%;
    background-color: #ccc;
    margin-right: 15px;
    padding: 15px;
}
.last {
    margin-right: 0;
}

JavaScript

$('.content .box:nth-child(3n)').addClass('last');