Sass @mixin and @include

The @mixin directive allows us to define a style that can be reused throughout the stylesheet.

The @include directive can incorporate the mixin into the document.

Defining a Mixin

The following example creates a mixin named "important-text":

Sass Code:

@mixin important-text {
  color: red;
  font-size: 25px;
  font-weight: bold;
  border: 1px solid blue;
}

Note: The hyphen - and the underscore _ are identical in Sass, meaning @mixin important-text { } and @mixin important_text { } are the same mixin.

Using a Mixin

The @include directive can be used to include a mixin:

Sass @include Mixin Syntax:

selector {
  @include mixin-name;
}

Thus, including the important-text mixin looks like this:

Example

.danger {
  @include important-text;
  background-color: green;
}

Converting the above code to CSS yields:

CSS Code:

.danger {
  color: red;
  font-size: 25px;
  font-weight: bold;
  border: 1px solid blue;
  background-color: green;
}

Mixins can also include other mixins, as shown below:

Example

@mixin special-text {
  @include important-text;
  @include link;
  @include special-border;
}

Passing Variables to Mixins

Mixins can accept parameters.

We can pass variables to mixins.

Define a mixin that can receive parameters:

Example

/* Mixin receiving two parameters */
@mixin bordered($color, $width) {
  border: $width solid $color;
}

.myArticle {
  @include bordered(blue, 1px);  // Call mixin with two parameters
}

.myNotes {
  @include bordered(red, 2px); // Call mixin with two parameters
}

The mixin parameters in the above example are for setting border properties (color and width).

Converting the above code to CSS yields:

CSS Code:

.myArticle {
  border: 1px solid blue;
}

.myNotes {
  border: 2px solid red;
}

Mixin parameters can also have default values, with the following syntax:

Example

@mixin bordered($color: blue, $width: 1px) {
  border: $width solid $color;
}

When including the mixin, you only need to pass the variable names and their values:

Example

@mixin sexy-border($color, $width: 1in) {
  border: {
    color: $color;
    width: $width;
    style: dashed;
  }
}
p { @include sexy-border(blue); }
h1 { @include sexy-border(blue, 2in); }

Converting the above code to CSS yields:

CSS Code:

p {
  border-color: blue;
  border-width: 1in;
  border-style: dashed;
}

h1 {
  border-color: blue;
  border-width: 2in;
  border-style: dashed;
}

Variable Arguments

Sometimes, it's not clear how many arguments a mixin or a function will use. In such cases, we can use ... to set variable arguments.

For example, a mixin for creating box-shadow can take any number of box-shadows as parameters.

Example

@mixin box-shadow($shadows...) {
      -moz-box-shadow: $shadows;
      -webkit-box-shadow: $shadows;
      box-shadow: $shadows;
}

.shadows {
  @include box-shadow(0px 4px 5px #666, 2px 6px 10px #999);
}

Converting the above code to CSS yields:

CSS Code:

.shadows {
  -moz-box-shadow: 0px 4px 5px #666, 2px 6px 10px #999;
  -webkit-box-shadow: 0px 4px 5px #666, 2px 6px 10px #999;
  box-shadow: 0px 4px 5px #666, 2px 6px 10px #999;
}

@include box-shadow(0px 4px 5px #666, 2px 6px 10px #999);
}

Convert the above code to CSS code as follows:

CSS Code:

.shadows {
  -moz-box-shadow: 0px 4px 5px #666, 2px 6px 10px #999;
  -webkit-box-shadow: 0px 4px 5px #666, 2px 6px 10px #999;
  box-shadow: 0px 4px 5px #666, 2px 6px 10px #999;
}

Using Prefix Mixins

Using prefix mixins is also very convenient, as shown in the following example:

Example

@mixin transform($property) {
  -webkit-transform: $property;
  -ms-transform: $property;
  transform: $property;
}

.myBox {
  @include transform(rotate(20deg));
}

Convert the above code to CSS code as follows:

CSS Code:

.myBox {
  -webkit-transform: rotate(20deg);
  -ms-transform: rotate(20deg);
  transform: rotate(20deg);
}