learnxinyminutes-docs/sass.html.markdown

language	contributors	filename
sass	Sean Corrales https://github.com/droidenator	learnsass.scss

Sass is a CSS pre-processor. It adds several features that plain CSS lacks such as variables, mixins, basic math, and inheritance.

Initially, Sass was written using spacing and indention instead of brackets and semi-colons; these files use the extension '.sass'. Sass was later revised to use brackets and semi-colons and become a superset of CSS3. This new version uses the extension ".scss". Using ".scss" means that any valid CSS3 file can be converted to Sass by simply changing the file extension to '.scss'.

If you're already familiar with CSS3, you'll be able to pick up Sass relatively quickly. It does not provide any new styling options but rather the tools to write your CSS more efficiently and make maintenance much easier.

Sass files must be compiled into CSS. You can use any number of commandline tools to compile Sass into CSS. Many IDEs also offer Sass compilation, as well.

/* Like CSS, Sass uses slash-asterisk to denote comments. Slash-asterisk comments 
   can span multiple lines. These comments will appear in your compiled CSS */

// Sass also supports single line comments that use double slashes. These comments will
// not be rendered in your compiled CSS

/* ####################
   ## VARIABLES
   #################### */

/* Sass allows you to define variables that can be used throughout
   your stylesheets. Variables are defined by placing a '$' in front 
   of a string. Many users like to keep their variables in a single file */
$primary-color: #0000ff;
$headline-size: 24px;

/* Variables can be used in any CSS declaration. This allows you to change
   a single value in one place. */
a {
  color: $primary-color;
}

h1 {
  color: $primary-color;
  font-size: $headline-size;
}

/* After compiling the Sass files into CSS, you'll have the following code
   in your generated CSS file */
   
a { 
  color: #0000ff;
}

h1 {
  color: #0000ff;
  font-size: 24px;
}

/* ####################
   ## NESTING
   #################### */
   
/* Nesting allows you to easily group together statements and nest them
   in a way that indicates their hierarchy */
article {
  font-size: 14px;
  
  a {
    text-decoration: underline; 
  }
  
  ul {
    list-style-type: disc;
    
    li {
      text-indent: 3em;
    }
  }
  
  pre, img {
    display: inline-block;
    float: left;
  }
}

/* The above will compile into the following CSS */
article {
  font-size: 14px;
}

article a {
  text-decoration: underline;
}

article ul {
  list-style-type: disc;
}

article ul li {
  text-indent: 3em;
}

article pre, 
article img {
  display: inline-block;
  float: left;
}

/* It is recommended to not nest too deeply as this can cause issues with
   specificity and make your CSS harder to work with and maintain. Best practices
   recommend going no more than 3 levels deep when nesting. */
   
/* ###############################
   ## REFERENCE PARENT SELECTORS
   ############################### */   
   
/* Reference parent selectors are used when you're nesting statements and want to 
   reference the parent selector from within the nested statements. You can reference
   a parent using & */
   
a {
  text-decoration: none;
  color: #ff0000;
  
  &:hover {
    text-decoration: underline;  
  }
  
  body.noLinks & {
    display: none;
  }
}

/* The above Sass will compile into the CSS below */

a {
  text-decoration: none;
  color: #ff0000;
}

a:hover {
  text-decoration: underline;
}

body.noLinks a {
  display: none;
}


/* ####################
   ## MIXINS
   #################### */
   
/* Mixins allow you to define reusable chunks of CSS. They can take one or more
   arguments to allow you to make reusable pieces of styling. Mixins can also
   be very helpful when dealing with vendor prefixes. */
   
@mixin form-button($color, $size, $border-radius) {
  color: $color;
  font-size: $size;
  border-radius: $border-radius;
}

/* Mixins are invoked within a CSS declaration. */

.user-form .submit {
  @include form-button(#0000ff, 16px, 4px);
}

/* The above mixin will compile into the following css */

.user-form .submit {
  color: #0000ff;
  font-size: 16px;
  border-radius: 4px;
}

/* ####################
   ## FUNCTIONS
   #################### */
   
/* Sass provides functions that can be used to accomplish a variety of tasks. Consider the following */
   
body {
  width: round(10.25px);    
}

.footer {
  background-color: fade_out(#000000, 0.25)
}

/* The above Sass will compile into the following CSS */

body {
  width: 10px;
}

.footer {
  background-color: rgba(0, 0, 0, 0.75);
}   
   
/* You may also define your own functions. Functions are very similar to mixins. When trying to choose between 
   a function or a mixin, remember that functions are best for returning values while mixins are best for 
   generating CSS while functions are better for logic that might be used throughout your Sass code. The
   examples in the Math Operators' section are ideal candidates for becoming a reusable function. */

/* This function will take a target size and the parent size and calculate and return the percentage */
   
@function calculate-percentage($target-size, $parent-size) {
  @return $target-size / $parent-size * 100%;
}

/* Functions can be invoked by using their name and passing in the required arguments */

$main-content: calculate-percentage(600px, 960px);

.main-content {
  width: $main-content;
}

.sidebar {
  width: calculate-percentage(300px, 960px);
}

/* The above Sass will compile into the following CSS */

.main-content {
  width: 62.5%;
}

.sidebar {
  width: 31.25%;
}

/* ####################
   ## EXTEND/INHERITANCE
   #################### */
   
/* Sass allows you to extend an existing CSS statement. This makes it 
   very easy to write CSS that does not violate DRY principles. Any
   CSS statement can be extended */
   
.content-window {
  font-size: 14px;
  padding: 10px;
  color: #000;
  border-radius: 4px;
}

.message-window {
  @extend .content-window;
  background-color: #0000ff;
}

.notification-window {
  @extend .content-window;
  background-color: #ff0000;
}

.settings-window {
  @extend .content-window;
  background-color: #ccc;
}

/* The above Sass will be compile into the following CSS */

.content-window,
.message-window,
.notification-window,
.settings-window {
  font-size: 14px;
  padding: 10px;
  color: #000;
  border-radius: 4px;
}

.message-window {
  background-color: #0000ff;
}

.notification-window {
  background-color: #ff0000;
}

.settings-window {
  background-color: #ccc;
}

/* Extending a CSS statement is preferable to creating a mixin 
   because of the way it groups together the classes that all share
   the same base styling. If this was done with a mixin, the font-size,
   padding, color, and border-radius would be duplicated for each statement
   that called the mixin. While it won't affect your workflow, it will
   add unnecessary bloat to the files created by the Sass compiler. */
   
/* #########################
   ## PLACEHOLDER SELECTORS
   ######################### */   
   
/* Placeholders are useful when creating a CSS statement to extend. If you wanted to create
   a CSS statement that was exclusively used with @extend, you can do so using a placeholder.
   Placeholders begin with a '%' instead of '.' or '#'. Placeholders will not appear in the 
   compiled CSS. */
   
%content-window {
  font-size: 14px;
  padding: 10px;
  color: #000;
  border-radius: 4px;
}

.message-window {
  @extend %content-window;
  background-color: #0000ff;
}

/* The above Sass would compile to the following CSS */

.message-window {
  font-size: 14px;
  padding: 10px;
  color: #000;
  border-radius: 4px;
}

.message-window {
  background-color: #0000ff;
}
      
/* ####################
   ## MATH OPERATIONS
   #################### */      
   
/* Sass provides the following operators: +, -, *, /, and %. These can
   be useful for calculating values directly in your Sass files instead
   of using values that you've already calculated by hand. Below is an example
   of a setting up a simple two column design. */
   
$content-area: 960px;
$main-content: 600px;
$sidebar-content: 300px;

$main-size: $main-content / $content-area * 100%;
$sidebar-size: $sidebar-content / $content-area * 100%;
$gutter: 100% - ($main-size + $sidebar-size);

body {
  width: 100%;
}

.main-content {
  width: $main-size;
}

.sidebar {
  width: $sidebar-size;
}

.gutter {
  width: $gutter;
}

/* The above Sass would compile to the CSS below */

body {
  width: 100%;
}

.main-content {
  width: 62.5%;
}

.sidebar {
  width: 31.25%;
}

.gutter {
  width: 6.25%;
}
   

Usage

Compatibility

Further Reading