Sass (style sheet language)

Sass was initially designed by Hampton Catlin and developed by Natalie Weizenbaum.^[6][7]

SassScript was implemented in multiple languages, the noteworthy implementations are:

• The official open-source Dart implementation.^[8]
• The official "sass" node module on npm, which is Dart Sass compiled to pure JavaScript.^[9]
• The official "sass-embedded" node module which is a JavaScript wrapper around the native Dart executable.^[10]
• The original open-source Ruby implementation created in 2006,^[8] since deprecated due to the lack of maintainers and reached End-of-Life in March 2019.^[11][12]
• libSass, the official open-source C++ implementation, deprecated in October 2020.^[13]
• The deprecated "node-sass" node module on npm, based on the deprecated libSass.^[14]
• JSass, an unofficial Java implementation,^[15] based on the deprecated libSass.^[16]
• phamlp, an unofficial Sass/SCSS implementation in PHP.^[8]
• Vaadin has a Java implementation of Sass.^[17]
• Firebug, a Firefox XUL ("legacy") extension for web development.^[18] It has been since deprecated in favor of developer tools integrated into Firefox itself. It stopped working since Firefox 57 dropped support for XUL extensions.

Sass allows variables to be defined. Variables begin with a dollar sign ($). Variable assignment is done with a colon (:).^[18]

SassScript supports four data types:^[18]

• Numbers (including units)
• Strings (with quotes or without)
• Colors (name, or names)
• Booleans

Variables can be arguments to or results from one of several available functions.^[19] During translation, the values of the variables are inserted into the output CSS document.^[2]

$primary-color: #3bbfce;
$margin: 16px;

.content-navigation {
  border-color: $primary-color;
  color: darken($primary-color, 10%);
}

.border {
  padding: $margin / 2;
  margin: $margin / 2;
  border-color: $primary-color;
}

$primary-color: #3bbfce
$margin: 16px

.content-navigation
  border-color: $primary-color
  color: darken($primary-color, 10%)

.border
  padding: $margin/2
  margin:  $margin/2
  border-color: $primary-color

:root{
    --primary-color:#3bbfce;
    --secondary-color:#2b9eab;
    --margin:8px;
}


.content-navigation {
  border-color: var(--secondary-color)
  color: var(--secondary-color);
}

.border {
  padding: 8px;
  margin: var(--margin);
  border-color: #3bbfce;
}

CSS does support logical nesting, but the code blocks themselves are not nested. Sass allows the nested code to be inserted within each other.^[2]

table.hl {
  margin: 2em 0;
  td.ln {
    text-align: right;
  }
}

li {
  font: {
    family: serif;
    weight: bold;
    size: 1.3em;
  }
}

table.hl 
  margin: 2em 0
  td.ln 
    text-align: right
  
li 
  font: 
    family: serif
    weight: bold
    size: 1.3em

table.hl {
  margin: 2em 0;
}
table.hl td.ln {
  text-align: right;
}

li {
  font-family: serif;
  font-weight: bold;
  font-size: 1.3em;
}

More complicated types of nesting including namespace nesting and parent references are discussed in the Sass documentation.^[18]

@mixin table-base {
  th {
    text-align: center;
    font-weight: bold;
  }
  td, th {
    padding: 2px;
  }
}

#data {
  @include table-base;
}

=table-base
  th
    text-align: center
    font-weight: bold
  td, th
    padding: 2px

#data
  +table-base

#data th {
  text-align: center;
  font-weight: bold;
}
#data td, #data th {
  padding: 2px;
}

Sass allows for iterating over variables using @for, @each and @while, which can be used to apply different styles to elements with similar classes or ids.

$squareCount: 4
@for $i from 1 to $squareCount 
  #square-#{$i} 
   background-color: red
   width: 50px * $i
   height: 120px / $i

#square-1 {
  background-color: red;
  width: 50px;
  height: 120px;
}

#square-2 {
  background-color: red;
  width: 100px;
  height: 60px;
}

#square-3 {
  background-color: red;
  width: 150px;
  height: 40px;
}

Mixins also support arguments.^[2]

=left($dist) 
  float: left
  margin-left: $dist

#data 
  +left(10px)

#data {
  float: left;
  margin-left: 10px;
}

=table-base
  th
    text-align: center
    font-weight: bold
  td, th 
    padding: 2px

=left($dist) 
  float: left
  margin-left: $dist

#data 
  +left(10px)
  +table-base

#data {
  float: left;
  margin-left: 10px;
}
#data th {
  text-align: center;
  font-weight: bold;
}
#data td, #data th {
  padding: 2px;
}

While CSS3 supports the Document Object Model (DOM) hierarchy, it does not allow selector inheritance. In Sass, inheritance is achieved by inserting a line inside of a code block that uses the @extend keyword and references another selector. The extended selector's attributes are applied to the calling selector.^[2]

.error
  border: 1px #f00
  background: #fdd

.error.intrusion 
  font-size: 1.3em
  font-weight: bold

.badError 
  @extend .error
  border-width: 3px

.error, .badError {
  border: 1px #f00;
  background: #fdd;
}

.error.intrusion,
.badError.intrusion {
  font-size: 1.3em;
  font-weight: bold;
}

.badError {
  border-width: 3px;
}

Sass supports multiple inheritance.^[18]

At the 2012 HTML5 Developer Conference, Hampton Catlin, the creator of Sass, announced version 1.0 of libSass, an open source C++ implementation of Sass developed by Catlin, Aaron Leung, and the engineering team at Moovweb.^[20][21]

According to Catlin, libSass can be "drop[ped] into anything and it will have Sass in it...You could drop it right into Firefox today and build Firefox and it will compile in there. We wrote our own parser from scratch to make sure that would be possible."^[22]

The design goals of libSass are:

• Performance – Developers have reported 10x speed up increases over the Ruby implementation of Sass.^[23]
• Easier integration – libSass makes it easier to integrate Sass into more software. Before libSass, tightly integrating Sass into a language or software product required bundling the entire Ruby interpreter. By contrast, libSass is a statically linkable library with zero external dependencies and C-like interface, making it easy to wrap Sass directly into other programming languages and tools. For example, open source libSass bindings now exist for Node, Go, and Ruby.^[21]
• Compatibility – libSass's goal is full compatibility with the official Ruby implementation of Sass. This goal has been achieved on libsass 3.3.^[24]

• Less (style sheet language)
• Stylus (style sheet language)

• Ndia, John Gichuki; Muketha, Geoffrey Muchiri; Omieno, Kelvin Kabeti (2019). "Complexity Metrics for Sassy Cascading Style Sheets" (PDF). Baltic Journal of Modern Computing. 7 (4). doi:10.22364/bjmc.2019.7.4.01.
• Cederholm, Dan (2013). Sass for Web Designers (PDF). A Book Apart. ISBN 978-1-937557-13-3.
• Watts, Luke (2016). Mastering Sass. Packt Publishing.

• Official website