Style Guides Using Sass @extend

There are some very common front-end development patterns that drive me crazy. CSS with every style related to a specific selector on one line and IE-only stylesheets with conditional comments are both common place and even encouraged by some. But the worst, in my opinion, is breaking our CSS into multiple files in an attempt to make them “themable.” Usually this results in something like a main.css and a fonts.css or colors.css. Having a go-to file for designers to manipulate fonts and colors is very useful, but usually the structure of this secondary file mirrors the primary file and you end up with a lot of repetition. Furthermore, if your DOM structure changes, then you will need to update multiple files (ie.css results in a similar problem).

Sass’ @extend feature allows us to have a style-guide.sass in which designers can run free, but is not dependent on DOM structure. Let’s take a look at how I setup my style guides.

The Style Guide
The designer on the project has put together a wonderful style guide PDF which I will be implementing in Sass. Here is what it looks like:

Style-guide-full

As you can see, each style has a title and some specifics for the text treatment.

First I setup variables for our color palatte.

$primary-orange:   #fe8a16
$hover-orange:     #f67502
$steel-blue:       #303b41 
$bright-blue:      #4892bc
$dark-grey:        #4b4b48

Next I create some simple mixins to handle usage of custom fonts.

=custom-font
  font-family: "Droid Sans"
  font-weight: normal
 
=bold-custom-font
  font-family: "Droid Sans Bold"
  font-weight: bold

Finally, I start defining the styles as classes. As you can see, I am using @extend to avoid repeating myself. I’m going to omit some of the styles in the guide for the sake of brevity.

.sg-heading-1
  +custom-font
  font-size: 32px
  line-height: 36px
  color: $steel-blue
 
.sg-heading-2
  @extend .sg-heading-1
  font-size: 20px
  line-height: 28px
 
.sg-heading-3
  @extend .sg-heading-2
  color: $bright-blue
 
.sg-main-body
  font-size: 14px
  line-height: 24px
  font-weight: normal
  color: $dark-grey
 
.sg-secondary-body
  @extend .sg-main-body
  font-size: 12px
  line-height: 18px
 
.sg-text-link-1
  font-weight: normal
  color: $primary-orange
  text-decoration: none
  &:hover
    color: $hover-orange

Referencing the Style Guide
Now, when I go to implement a specific portion of the site, I can be concise by referencing the style guide.

.info-box
  h2
    @extend .sg-heading-2
  ul li
    @extend .sg-text-link-1
  p
    @extend .sg-main-body
  dl
    @extend .sg-secondary-body

Here’s the resulting CSS output:

.sg-heading-1, .sg-heading-2, .sg-heading-3, .info-box h2 {
  font-family: "Droid Sans";
  font-weight: normal;
  font-size: 32px;
  line-height: 36px;
  color: #303b41; }
 
.sg-heading-2, .sg-heading-3, .info-box h2 {
  font-size: 20px;
  line-height: 28px; }
 
.sg-heading-3 {
  color: #4892bc; }
 
.sg-main-body, .sg-secondary-body, .info-box dl, .info-box p {
  font-size: 14px;
  line-height: 24px;
  font-weight: normal;
  color: #4b4b48; }
 
.sg-secondary-body, .info-box dl {
  font-size: 12px;
  line-height: 18px; }
 
.sg-text-link-1, .info-box ul li {
  font-weight: normal;
  color: #fe8a16;
  text-decoration: none; }
  .sg-text-link-1:hover, .info-box ul li:hover {
    color: #f67502; }

Conclusion
I have been incredibly happy with this approach. It has all the independence of the external fonts-and-colors.css method, but is more flexible, uses less code and is more readable in both the Sass and CSS forms.

I highly suggest getting your designer to build a style guide. It enforces consistency and keeps the randomness out of coding. Why should a site use every font size between 12px and 22px? Just pick a few sizes and standardize on them.

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