sass进阶 @if @else if @else @for循环

@mixin blockOrHidden($boolean:true) {
  @if $boolean {
      @debug "$boolean is #{$boolean}";
      display: block;
    }
  @else {
      @debug "$boolean is #{$boolean}";
      display: none;
    }
}

.block {
  @include blockOrHidden;
}

.hidden{
  @include blockOrHidden(false);
}

.block {
  display: block;
}

.hidden {
  display: none;
}

@for $i from <start> through <end>
@for $i from <start> to <end>