Sass Scss

Fundumentals

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SASS Fundamentals: Getting Started

SASS (Syntactically Awesome Style Sheets) is a popular CSS preprocessor that adds power and elegance to basic CSS. It helps write maintainable, DRY (Don't Repeat Yourself) code that compiles into standard CSS for browsers.

Core Concepts

Preprocessing:
- You write code in a SASS syntax (SCSS or the older indented Sass syntax).
- A SASS compiler processes this code.
- Output: Standard CSS file that browsers can understand.
graph LR A[Write SCSS/Sass Code] --> B(SASS Compiler); B --> C[Generate Standard CSS]; C --> D{Browser Renders Styles};

Variables:

Store reusable values like colors, fonts, or spacing units.
Syntax: Use the $ symbol followed by the variable name.
Benefit: Easy updates – change the value in one place, and it reflects everywhere.

Example:

// Define variables
$primary-color: #3498db;
$base-font-size: 16px;

// Use variables
body {
  font-size: $base-font-size;
  color: $primary-color;
}

.button {
  background-color: $primary-color;
  font-size: $base-font-size * 0.9; // Use operators
}

Nesting:

Mimic the structure of your HTML by nesting CSS selectors.
Benefit: Improves readability and organization by grouping related styles.

Example:

// SCSS with Nesting
nav {
  ul {
    margin: 0;
    padding: 0;
    list-style: none;

    li {
      display: inline-block;

      a {
        text-decoration: none;
        color: $primary-color; // Using variable from above

        &:hover { // Use '&' to reference the parent selector
          text-decoration: underline;
        }
      }
    }
  }
}

Compiled CSS Output:

nav ul {
  margin: 0;
  padding: 0;
  list-style: none;
}
nav ul li {
  display: inline-block;
}
nav ul li a {
  text-decoration: none;
  color: #3498db;
}
nav ul li a:hover {
  text-decoration: underline;
}

Getting Started Checklist

Install a SASS compiler (e.g., Dart Sass via npm: npm install -g sass).
Create an SCSS file (e.g., styles.scss).
Write your styles using SASS features.
Compile your SCSS file to CSS: sass styles.scss styles.css.
Link the compiled styles.css file in your HTML.

Intermediate

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SASS Intermediate: Reusability and Organization

Moving beyond the basics, SASS offers powerful tools for creating reusable code patterns and organizing large stylesheets effectively.

1. Partials and `@import`

Partials: SASS files named with a leading underscore (e.g., _variables.scss, _buttons.scss). They are not compiled into separate CSS files on their own.
@import: Used to include the contents of one SASS file (often a partial) into another.
Benefit: Break down large stylesheets into smaller, manageable, and modular files based on features or components. Note: Newer projects often prefer @use (see Advanced note).

Example File Structure:

styles/
|-- main.scss         # Main file, imports others
|-- _variables.scss   # Contains variable definitions
|-- _base.scss        # Basic styles (reset, typography)
|-- _components/
|   |-- _buttons.scss
|   |-- _cards.scss

main.scss:

// Import variables first
@import 'variables';

// Import base styles
@import 'base';

// Import components
@import 'components/buttons';
@import 'components/cards';

// Styles specific to main.scss
body {
  background-color: #f0f0f0;
}

2. Mixins (`@mixin`, `@include`)

@mixin: Defines a reusable block of styles, similar to a function in programming. Can accept arguments for flexibility.
@include: Includes the styles defined by a mixin into a selector.
Benefit: Perfect for applying common patterns (like vendor prefixes, complex backgrounds, or common layout structures) without duplicating code.

Example:

// Define a mixin for centering content
@mixin flex-center($direction: row) { // Argument with a default value
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: $direction;
}

// Define a mixin for transitions
@mixin transition($property: all, $duration: 0.3s, $timing: ease) {
  transition: $property $duration $timing;
  -webkit-transition: $property $duration $timing; // Example vendor prefix
}

// Use the mixins
.container {
  @include flex-center(column); // Use column direction
}

.button {
  @include flex-center; // Use default direction (row)
  @include transition(background-color); // Use specific property
}

3. Extend (`@extend`)

@extend: Allows one selector to inherit the styles of another selector.
Benefit: Groups selectors that share the exact same style block in the final CSS, potentially reducing file size.
Placeholder Selectors (%): Selectors starting with % (e.g., %message-shared) are not output in the CSS unless they are extended. Ideal for creating base styles intended only for inheritance.

Example:

// Define a placeholder for shared alert styles
%alert-base {
  padding: 15px;
  margin-bottom: 20px;
  border: 1px solid transparent;
  border-radius: 4px;
}

.alert-success {
  @extend %alert-base; // Inherit base styles
  color: #3c763d;
  background-color: #dff0d8;
  border-color: #d6e9c6;
}

.alert-danger {
  @extend %alert-base; // Inherit base styles
  color: #a94442;
  background-color: #f2dede;
  border-color: #ebccd1;
}

Compiled CSS Output (Simplified):

/* %alert-base styles are merged into extending selectors */
.alert-success, .alert-danger {
  padding: 15px;
  margin-bottom: 20px;
  border: 1px solid transparent;
  border-radius: 4px;
}

.alert-success {
  color: #3c763d;
  background-color: #dff0d8;
  border-color: #d6e9c6;
}

.alert-danger {
  color: #a94442;
  background-color: #f2dede;
  border-color: #ebccd1;
}

Caution with @extend: Overuse, especially across different files or with complex selectors, can sometimes lead to unexpected generated CSS and large selector groups. Mixins are often preferred for complex reusable patterns.

Advanced

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SASS Advanced: Logic, Functions, and Modules

Advanced SASS features unlock programmatic capabilities, allowing for complex logic, custom calculations, and a more robust, modern approach to managing dependencies.

1. Control Directives (`@if`, `@for`, `@each`, `@while`)

These allow you to introduce logic directly into your stylesheets.

@if/@else if/@else: Conditionally apply styles based on expressions (often involving variables).

@mixin theme-styles($theme: light) {
  @if $theme == dark {
    background-color: #333;
    color: #eee;
  } @else {
    background-color: #fff;
    color: #333;
  }
}
.widget { @include theme-styles(dark); }

@for: Loop through a range of numbers to generate repetitive styles.

// Generate grid column classes
@for $i from 1 through 12 { // 'through' is inclusive
  .col-#{$i} { // Use interpolation #{...}
    width: percentage($i / 12);
  }
}

@each: Iterate over items in a list or map.

$colors: (primary: #007bff, success: #28a745, danger: #dc3545);

@each $name, $color in $colors {
  .button-#{$name} {
    background-color: $color;
    &:hover {
      background-color: darken($color, 10%); // Using a built-in function
    }
  }
}

@while: Repeat styles as long as a condition is true (less common than @for or @each).

2. Custom Functions (`@function`, `@return`)

Define your own reusable calculations or value manipulations.
Functions take arguments and must return a value using @return.

Example: Calculate REM values

$base-font-size: 16px; // Base size in pixels

@function rem($pixels) {
  @if unitless($pixels) {
    // Assume pixels if no unit provided
    @return ($pixels / $base-font-size) * 1rem;
  } @else if unit($pixels) == 'px' {
    @return ($pixels / $base-font-size) * 1rem;
  } @else {
    @error "Function rem() expects a pixel value.";
  }
}

body {
  font-size: $base-font-size; // Sets the base for rem calculations
}

h1 {
  font-size: rem(32px); // Output: 2rem
  margin-bottom: rem(20); // Output: 1.25rem (unitless input assumed px)
}

3. Modern Module System (`@use`, `@forward`)

This system is the recommended replacement for @import in modern SASS projects. It offers better control over scope and dependencies.

@use: Loads styles, functions, and variables from another module (file). Crucially, it namespaces the imported members by default (based on the filename). This prevents naming collisions.

graph LR A[styles.scss] -- @use 'variables' as vars --> B[_variables.scss]; A -- @use 'components/button' --> C[_button.scss]; B -- defines $primary-color --> A; C -- defines .button-base --> A; subgraph Module Scope direction LR B --- |Namespace: variables| A; C --- |Namespace: button| A; end

_variables.scss:
```
$primary-color: #007bff;
$base-padding: 10px;
```
_button.scss:
```
@use 'variables' as vars; // Load variables with namespace 'vars'

.button {
  padding: vars.$base-padding;
  background-color: vars.$primary-color;
}
```
main.scss:
```
@use 'variables' as v; // Use 'v' as namespace
@use 'button'; // Use default 'button' namespace

body {
  padding: v.$base-padding * 2; // Access variable via namespace
}

// Styles from button module are included automatically
```

@forward: Makes members (variables, mixins, functions) from another module available to files that @use the current module. It acts like a "pass-through". Often used in intermediary files (like _index.scss within a component folder) to expose specific members publicly.

_components/_index.scss:

@forward 'button'; // Make everything from _button.scss available
@forward 'card' hide $internal-card-variable; // Forward card, but hide internal variable

main.scss:

@use 'components'; // Uses _components/_index.scss by default

.my-button {
  @extend .button; // Can extend button class forwarded from index
}

4. Built-in Modules

SASS provides powerful built-in modules (loaded via @use) for common tasks:

sass:math: Advanced mathematical functions (math.sqrt(), math.pow(), etc.).
sass:color: Manipulate colors (adjust hue, saturation, lightness, opacity, mix colors).
sass:string: String manipulation functions.
sass:list, sass:map, sass:selector: Functions for working with SASS data types and selectors.

Example using sass:color:

@use 'sass:color';

$base-color: #3498db;

.button-primary {
  background-color: $base-color;
  &:hover {
    // Make the button 10% darker on hover
    background-color: color.adjust($base-color, $lightness: -10%);
  }
  &:active {
    // Make the button 50% transparent on active
    background-color: color.adjust($base-color, $alpha: -0.5);
  }
}

By mastering these advanced features, you can write highly efficient, scalable, and maintainable CSS codebases.

Children

Sass Scss

SASS Fundamentals: Getting Started

Core Concepts

Getting Started Checklist

SASS Intermediate: Reusability and Organization

1. Partials and @import

2. Mixins (@mixin, @include)

3. Extend (@extend)

SASS Advanced: Logic, Functions, and Modules

1. Control Directives (@if, @for, @each, @while)

2. Custom Functions (@function, @return)

3. Modern Module System (@use, @forward)

4. Built-in Modules

1. Partials and `@import`

2. Mixins (`@mixin`, `@include`)

3. Extend (`@extend`)

1. Control Directives (`@if`, `@for`, `@each`, `@while`)

2. Custom Functions (`@function`, `@return`)

3. Modern Module System (`@use`, `@forward`)