Sass is a powerful CSS preprocessor that allows developers to write more efficient and maintainable CSS code. One of the key features of Sass is introspection, which allows developers to inspect and manipulate Sass code at runtime.
Introspection is the ability of a programming language to examine and modify its own code at runtime. In Sass, introspection is achieved through a set of built-in functions that allow developers to query and manipulate Sass code.
One of the most commonly used introspection functions in Sass is variable-exists(), which allows developers to check if a variable has been defined in their Sass code. For example:
<!-- SCSS -->
$primary-color: #007bff;
@if variable-exists('primary-color') {
body {
background-color: $primary-color;
}
}
<!-- Compiled CSS -->
body {
background-color: #007bff;
}In this example, the variable-exists() function is used to check if the $primary-color variable has been defined. If the variable exists, the background color of the body element is set to the value of the variable.
Another useful introspection function in Sass is type-of(), which allows developers to check the data type of a Sass value. For example:
<!-- SCSS -->
$primary-color: #007bff;
@if type-of($primary-color) == color {
body {
background-color: $primary-color;
}
}
<!-- Compiled CSS -->
body {
background-color: #007bff;
}In this example, the type-of() function is used to check if the $primary-color variable is a color value. If the variable is a color, the background color of the body element is set to the value of the variable.
Sass also provides a set of introspection functions for working with lists and maps. For example, the length() function can be used to get the length of a list or map:
<!-- SCSS -->
$colors: (
primary: #007bff,
secondary: #6c757d,
success: #28a745,
danger: #dc3545,
warning: #ffc107,
info: #17a2b8,
light: #f8f9fa,
dark: #343a40
);
@if length($colors) > 0 {
.color-list {
display: flex;
flex-wrap: wrap;
}
@each $name, $color in $colors {
.color-item--#{$name} {
background-color: $color;
width: 100px;
height: 100px;
margin: 10px;
}
}
}
<!-- Compiled CSS -->
.color-list {
display: flex;
flex-wrap: wrap;
}
.color-item--primary {
background-color: #007bff;
width: 100px;
height: 100px;
margin: 10px;
}
.color-item--secondary {
background-color: #6c757d;
width: 100px;
height: 100px;
margin: 10px;
}
.color-item--success {
background-color: #28a745;
width: 100px;
height: 100px;
margin: 10px;
}
.color-item--danger {
background-color: #dc3545;
width: 100px;
height: 100px;
margin: 10px;
}
.color-item--warning {
background-color: #ffc107;
width: 100px;
height: 100px;
margin: 10px;
}
.color-item--info {
background-color: #17a2b8;
width: 100px;
height: 100px;
margin: 10px;
}
.color-item--light {
background-color: #f8f9fa;
width: 100px;
height: 100px;
margin: 10px;
}
.color-item--dark {
background-color: #343a40;
width: 100px;
height: 100px;
margin: 10px;
}In this example, the length() function is used to check if the $colors map contains any items. If the map contains items, a list of color swatches is generated using the @each directive.
Introspection is a powerful feature of Sass that allows developers to write more flexible and maintainable code. By using introspection functions, developers can write code that adapts to changing requirements and data.