Полезные миксины

usefull_mixins.scss

/*********************************************************STRING REPLACE************************************************************/
@function str-replace($string, $search, $replace: '') {
  $index: str-index($string, $search);
  
  @if $index {
    @return str-slice($string, 1, $index - 1) + $replace + str-replace(str-slice($string, $index + str-length($search)), $search, $replace);
  }
  
  @return $string;
}
$str-replace: str-replace('(100%-5x)','x','10'); // "(100%-510)"

/*********************************************************INSERT STRING************************************************************/
@function insert-string($string, $replace: '', $search...) {
  @each $ext in $search {
    $index: str-index($string, $ext);

    @if $index {
      @return str-slice($string, 1, $index - 1) + $replace + str-slice($string, $index, str-length($string));
    }
  }
  @return $string;
}
$filename: '../images/best-image-ever.png';
$src: insert-string($filename, '__', '.png', '.jpg', '.other-extension'); // ../images/best-image-ever__.png

/*********************************************************CONVERT STRING TO NUMBER************************************************************/
@function _length($number, $unit) {
  $strings: 'px' 'cm' 'mm' '%' 'ch' 'pica' 'in' 'em' 'rem' 'pt' 'pc' 'ex' 'vw' 'vh' 'vmin' 'vmax';
  $units:   1px  1cm  1mm  1%  1ch  1pica  1in  1em  1rem  1pt  1pc  1ex  1vw  1vh  1vmin  1vmax;
  $index: index($strings, $unit);

  @if not $index {
    @warn "Unknown unit `#{$unit}`.";
    @return false;
  }

  @return $number * nth($units, $index);
}

@function number($string) {
  $strings: '0' '1' '2' '3' '4' '5' '6' '7' '8' '9';
  $numbers:  0   1   2   3   4   5   6   7   8   9;
  $result: 0;
  $minus: false;
  $divider: 0;
  @for $i from 1 through str-length($string) {
    $character: str-slice($string, $i, $i);
    $index: index($strings, $character);
    @if $character == '-' {
      $minus: true;
    }
    @else if $character == '.' {
      $divider: 1;
    }    
    @else {
      @if not $index {
        $result: if($minus, $result * -1, $result);
        @return _length($result, str-slice($string, $i));        
      }
      $number: nth($numbers, $index);
      // Decimal dot hasn't been found yet
      @if $divider == 0 {
        $result: $result * 10;
      }

      // Decimal dot has been found
      @else {
        // Move the decimal dot to the left
        $divider: $divider * 10;
        $number: $number / $divider;
      }
      $result: $result + $number;      
    }
    
  }
  @return if($minus, $result * -1, $result);
  @return $result;
}

.sass {
  cast: number("-15")+10;    //5
  cast: number("-1");     // -1
  cast: number("-0.5");    // -.5
  cast: number("-0");     // 0
  cast: number("0");      // 0
  case: number(".10");    // 0.1
  cast: number("1");      // 1
  cast: number("1.5");    // 1.5
  cast: number("10.");    // 10
  cast: number("12.380"); // 12.38
  cast: number("42");     // 42
  cast: number("1337");   // 1337

  cast: number("-10px");  // -10px
  cast: number("20em");   // 20em
  cast: number("30ch");   // 30ch

  cast: number("1fail");  // Error
  cast: number("string"); // Error