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HTML

              
                 <h1>Custom properties
  <br>applied safely</h1>
 <small>(Even for old browsers)</small>
              
            
!

CSS

              
                // gets a specific value from the fake custom properties map
// $vars is the map, you could find it @ variables.scss
@function getCSSvar($key){
  @if map-has-key($vars, $key){
    @return map-get($vars, $key);
  } @else {
    @warn $key + ' is not a valid variable name';
    // Lime is an horrible & not undercover color so it is perfect to highlight an error
    @return unquote('lime');
  }
} 

// cssVars( <[map]>(<[ property ]>: <[ value ]>)  )
//
// get a given map
// the mixin loops through it and get from the original variables map
// the current value and apply it using a single value and 
// a custom property with its fallback so it is available for all browsers
//
// .element {
//   @include cssVars(
//    (
//      background-color: --primary-color, 
//      color: --secondary-color
//    )
//  );
// }
//
@mixin cssVars($map) {
  @if (type-of($map) == 'map') {
    @each $prop in $map {
      $key: nth($prop, 1);
      $value: nth($prop, 2);
      
      $var: getCSSvar($value);
  
      #{$key}: $var;
      #{$key}: var(#{$value}, $var);
    }
  } @else {
    @warn 'Consider to use a MAP instead of a ' + type-of($map) + 'u son of a ...';
    
    @if type-of($map == 'list') {
      $key: nth($map, 1);
      $value: nth($map, 2);
      
      $var: getCSSvar($value);
  
      #{$key}: $var;
      #{$key}: var(#{$value}, $var);
    }
  }
}

// Custom Properties Map
// -----------
$vars: (
  --primary-color: #B23A68,
  --secondary-color: #A67499,
  --tertiary-color: #3b3b3b,
  --padded: 2rem,
  --border: 2px solid #333
);

*,
*:after,
*:before {
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    box-sizing: inherit;
    font-family: 'Franklin Gothic Medium', sans-serif
}

body {
  // using as a list
  @include cssVars((background, --tertiary-color));
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  
  h1 {
    // using as a map w/ multiple registers
    @include cssVars((
      color: --secondary-color,
      padding: --padded,
      border-bottom: --border
    ));
    text-align: center;
  }
  
  small {
    // using as a map w/ 1 register
    @include cssVars((color: --secondar-color));  // this variable does not exist
    margin: 0;
  }
}

              
            
!

JS

              
                
              
            
!
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