@mixin box-shadow($shadow...) {
    @if $enable-shadows {
      $result: ();
  
      @if (length($shadow) == 1) {
        // We can pass `@include box-shadow(none);`
        $result: $shadow;
      } @else {
        // Filter to avoid invalid properties for example `box-shadow: none, 1px 1px black;`
        @for $i from 1 through length($shadow) {
          @if nth($shadow, $i) != "none" {
            $result: append($result, nth($shadow, $i), "comma");
          }
        }
      }
      @if (length($result) > 0) {
        box-shadow: $result;
      }
    }
  }