Camelonta CSS / Sass Styleguide

A slightly modified version of the styleguide from Airbnb.

Table of Contents

1. Terminology - Rule Declaration - Selectors - Properties
2. CSS - Formatting - Comments - Atomic Design, ITCSS, BEM - ID Selectors - Border
3. Sass - Syntax - Ordering - Variables - Variable naming - Mixins - Extend directive - Nested selectors - Media queries

Terminology

Rule declaration

A “rule declaration” is the name given to a selector (or a group of selectors) with an accompanying group of properties. Here's an example:

.listing {
  font-size: 18px;
  line-height: 1.2;
}

Selectors

In a rule declaration, “selectors” are the bits that determine which elements in the DOM tree will be styled by the defined properties. Selectors can match HTML elements, as well as an element's class, ID, or any of its attributes. Here are some examples of selectors:

.my-element-class {
  /* ... */
}

[aria-hidden] {
  /* ... */
}

Properties

Finally, properties are what give the selected elements of a rule declaration their style. Properties are key-value pairs, and a rule declaration can contain one or more property declarations. Property declarations look like this:

/* some selector */ {
  background: #f1f1f1;
  color: #333;
}

CSS

Formatting

• Prefer dashes over camelCasing in class names.
  • Underscores are okay if you are using BEM
• Do not use ID selectors
• When using multiple selectors in a rule declaration, give each selector its own line.
• Put a space before the opening brace { in rule declarations
• In properties, put a space after, but not before, the : character.
• Put closing braces } of rule declarations on a new line
• Put blank lines between rule declarations

Bad

.avatar{
    border-radius:50%;
    border:2px solid white; }
.no, .nope, .not_good {
    // ...
}
#lol-no {
  // ...
}

Good

.avatar {
  border-radius: 50%;
  border: 2px solid white;
}

.one,
.selector,
.per-line {
  // ...
}

Comments

• Prefer line comments (// in Sass-land) to block comments.
• Prefer comments on their own line. Avoid end-of-line comments.
• Write detailed comments for code that isn't self-documenting:
  • Uses of z-index
  • Compatibility or browser-specific hacks

Atomic Design, ITCSS, BEM

We encourage some combinations of BEM, ITCSS and Atomic design for these reasons:

• It helps create clear, strict relationships between CSS and HTML
• It allows for less nesting and lower specificity
• It helps in building scalable stylesheets

Atomic design is a methodology for creating design systems.

• Short demo of Atomic design Play video
• Post by Brad Frost
• A CSS Architecture Worth Loving BEM & Atomic

ITCSS is a scalable and maintainable css architecture

• What is ITCSS?

BEM, or “Block-Element-Modifier”, is a naming convention for classes in HTML and CSS. It was originally developed by Yandex with large codebases and scalability in mind, and can serve as a solid set of guidelines for implementing OOCSS.

• CSS Trick's BEM 101
• Harry Roberts' introduction to BEM

We recommend a variant of BEM with hyphen-separated-lowercase “blocks”.

Example

<div class="listing-card">
  <h1 class="listing-card__title>Nice day in Stockholm, eh?</h1>
  <div class="listing-card__content">
    <p>With an average temperature of -35°c the Swedes are rushing to get the best spot at the beach. While having a fika, eating surströmming and shopping at Ikea inbetween.</p>
  </div>
  <a href="#" class="listing-card__link">Read more</a>
</div>

/* listing-card.scss */
.listing-card { }
.listing-card--featured { }
.listing-card__title { }
.listing-card__content { }

• .listing-card is the “block” and represents the higher-level component
• .listing-card__title is an “element” and represents a descendant of .listing-card that helps compose the block as a whole.
• .listing-card--featured is a “modifier” and represents a different state or variation on the .listing-card block.

Putting it together with Atomic, ITCSS & BEM

ID selectors

While it is possible to select elements by ID in CSS, it should generally be considered an anti-pattern. ID selectors introduce an unnecessarily high level of specificity to your rule declarations, and they are not reusable.

For more on this subject, read CSS Wizardry's article on dealing with specificity.

Border

Use 0 instead of none to specify that a style has no border.

Bad

.foo {
  border: none;
}

Good

.foo {
  border: 0;
}

Sass

Syntax

• Use the .scss syntax, never the original .sass syntax
• Order your regular CSS and @include declarations logically (see below)

Ordering of property declarations

1. Property declarations

   List all standard property declarations, anything that isn't an @include or a nested selector.

   .button-green {
     background: green;
     font-weight: bold;
     // ...
   }

2. @include declarations

   Grouping @includes at the end makes it easier to read the entire selector.

   .button-green {
     background: green;
     font-weight: bold;
     @include transition(background 0.5s ease);
     // ...
   }

3. Nested selectors

   Nested selectors, if necessary, go last, and nothing goes after them. Add whitespace between your rule declarations and nested selectors, as well as between adjacent nested selectors. Apply the same guidelines as above to your nested selectors.

   .button {
     background: green;
     font-weight: bold;
     @include transition(background 0.5s ease);
   
     .icon {
       margin-right: 10px;
     }
   }

Variables

Prefer dash-cased variable names (e.g. $my-variable) over camelCased or snake_cased variable names. It is acceptable to prefix variable names that are intended to be used only within the same file with an underscore (e.g. $_my-variable).

Variable naming

For naming color-variables we recommend using "real" names generated by Name Those Colors with an inline-comment describing the color.

Bad

$yellow: #dde80c;
$light-yellow: #eefa03;
$lighter-yellow: #edf728;

Good

$bitter-lemon: #dde80c; // Dark yellow
$chartreuse-yellow: #eefa03; // Yellow
$golden-fizz: #edf728; // Light yellow

Mixins

Mixins should be used to DRY up your code, add clarity, or abstract complexity--in much the same way as well-named functions. Mixins that accept no arguments can be useful for this, but note that if you are not compressing your payload (e.g. gzip), this may contribute to unnecessary code duplication in the resulting styles.

Extend directive

@extend should be avoided because it has unintuitive and potentially dangerous behavior, especially when used with nested selectors. Even extending top-level placeholder selectors can cause problems if the order of selectors ends up changing later (e.g. if they are in other files and the order the files are loaded shifts). Gzipping should handle most of the savings you would have gained by using @extend, and you can DRY up your stylesheets nicely with mixins.

Nested selectors

Do not nest selectors more than three levels deep!

.page-container {
  .content {
    .profile {
      // STOP!
    }
  }
}

When selectors become this long, you're likely writing CSS that is:

• Strongly coupled to the HTML (fragile) —OR—
• Overly specific (powerful) —OR—
• Not reusable

Again: never nest ID selectors!

If you must use an ID selector in the first place (and you should really try not to), they should never be nested. If you find yourself doing this, you need to revisit your markup, or figure out why such strong specificity is needed. If you are writing well formed HTML and CSS, you should never need to do this.

Media queries

Media queries for a specific component should be set in the component's file.

Bad

/* listing-card.scss */
.listing-card {
  float:left;
}


/* all-media-queries.scss */
@media (max-width: 600px) {
  .listing-card {
    float:none;
  }
}

Good

/* listing-card.scss */
.listing-card {
  float:left;
}

@media (max-width: 600px) {
  .listing-card {
    float:none;
  }
}

Is CSS broken?

CSS isn't broken. But it does require study and skill. It does require careful thought. As with anything in programming, you can make a mess of the code. Sure, blaming the language is the easy way out. But when your JavaScript is confusing and buggy, you know it’s not the language’s fault.