Popular bad way to use a function for media queries

Common but not recommended way to use a respond-to function

@mixin respond-to($media) {
  @if $media == desktop {
    @media (min-width: 960px) {
      @content;
    }
  } @else if $media == tablet {
    @media (min-width: 768px) {
      @content;
    }
  }
}

.factory {
  width: 100%;
  @include respond-to(desktop) {
    width: percentage(600px / 960px);
  }
  @include respond-to(tablet) {
    width: 50%;
  }
}