The ‘nav’ abstraction

Written by Harry Roberts on CSS Wizardry.

This post comes in a similar vein to Nicole Sullivan’s genius The media object saves hundreds of lines of code.

An abstraction is basically removing a pattern from a specific idea and making a more generic idea out of it. That is to say, rather than writing the same similar patterns over and over, create a single more generic representation of those patterns and reuse that instead.

Nicole does this with her media block by taking a series of similarly constructed but different components and sharing their common aspects in a more generic way. This is a really sensible and useful abstraction whereby she can make a pretty much infinite amount of pretty different blocks of content using only the same handful of lines of CSS each time. Genius!

Her media block abstraction is a pretty common one, and one I’ve used myself. Today I’m going to share another abstraction that may well be even more common and hopefully just as handy; the nav abstraction.

I’m sure you’ve had loads of projects where you’ve had a horizontal nav, and also maybe a breadcrumb trail and possibly a list of logos that go in a banner-style list…?

If this is the case then I also imagine you might have written something like:

#nav{
  list-style:none;
  margin-left:0;
}
#nav li{
  display:inline;
}
#nav a{
  ...
  [styles]
  ...
}


.breadcrumb{
  list-style:none;
  margin-left:0;
}
.breadcrumb li{
  display:inline;
}
.breadcrumb a{
  ...
  [styles]
  ...
}


.sponsors{
  list-style:none;
  margin-left:0;
}
.sponsors li{
  display:inline;
}
.sponsors a{
  ...
  [styles]
  ...
}

Here we can see that, although we’re building three different things, we’re reusing quite a few repeated patterns to create similar looking things. We need an abstraction.

The nav abstraction

Now, I’m not sure whether nav is actually the best word to use; these three examples are all types of navigational constructs, but that’s more coincidence than anything else. As such I encourage you to please offer up your alternative recommendations in the comments, please!

What we need to do now is take out the shared patterns and create a fourth class of .nav:

.nav{
    list-style:none;
    margin-left:0;
}
    .nav > li,
        .nav > li > a{
            display:inline-block;
           *display:inline;
            zoom:1;
    }

Here we define our abstraction. We take the repeated bits and make the most granular construct we can. Notice that we give both list items and links display:inline-block;, and include the IE7 hack to force elements to act like inline-block if they do not naturally support it.

This will throw any list into a very basic/crude horizontal series of links which we can then extend to adopt more specific styles, like so:

.nav{
    list-style:none;
    margin-left:0;
}
    .nav > li,
        .nav > li > a{
            display:inline-block;
           *display:inline;
            zoom:1;
    }


.site-nav{
    width:100%;
    background:#eee;
}
        .site-nav a{
            padding:5px 10px;
        }


.breadcrumb{}
    .breadcrumb li:before{
        content:"» "
    }
    .breadcrumb li:first-child:before{
        content:normal;
    }


.sponsors{
  text-align:center;
}

Using a base abstraction and then extending it we can create our breadcrumb with this HTML:

<ol class="nav  breadcrumb">
    <li><a href="/">Home</a></li>
    <li><a href="/about/">About</a></li>
    <li><a href="/about/us/">About us</a></li>
</ol>

Writing abstractions gives smaller CSS, removes unnecessary repetitions and makes simple elements of your design much more reusable. Nice!

By Harry Roberts

Harry Roberts is an independent consultant web performance engineer. He helps companies of all shapes and sizes find and fix site speed issues.

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