比较字符串SCSS值

Question

我想防止重复/覆盖CSS定义。 在我的示例中，我在mixins headlineTypo中定义了默认值。如果@include headlineTypo中的值为null，则默认情况下font-weight为700。 当我声明一个新的CSS类（标题中等）时，$ weight将设置默认值，所以我有：

.headline { font-size:12px ; font-weight: 700 }
.headline-medium { font-size:19px; font-weight: 700 }


@if ($weight != null) and (type-of($weight) == '700') {
    font-weight: $weight;
  } @else {
    font-weight: 700; // Set default
  }

@mixin headlineTypo($size: null, $weight: null) {  
  @if $size != null {
    font-size: $size;
  } @else {
    font-size: 24px; // Set default
  }

  @if ($weight != null) and ($weight != 700) {
    font-weight: $weight;
  } @else {
    font-weight: 700; // Set default
  }
}

.headline {
   @include headlineTypo(12px, null); // overwrite $size 
   &-medium {
      @include headlineTypo(19px, null); // overwrite $size
   }
}