//1px的实现

border($border-width = 1px, $border-color = #ccc, $border-style = solid, $radius = )

  // 为边框位置提供定位参考

  position: relative;

  if $border-width == null

    $border-width: ;

  border-radius: $radius;

  &::after

    // 用以解决边框layer遮盖内容

    pointer-events: none;

    position: absolute;

    z-index: ;

    top: ;

    left: ;

    // fix当元素宽度出现小数时，边框可能显示不全的问题

    // overflow: hidden;

    content: "\0020";

    border-color: $border-color;

    border-style: $border-style;

    border-width: $border-width;

    // 适配dpr进行缩放

    @media (max--moz-device-pixel-ratio: 1.49), (-webkit-max-device-pixel-ratio: 1.49), (max-device-pixel-ratio: 1.49), (max-resolution: 143dpi), (max-resolution: .49dppx)

      width: %;

      height: %;

      if $radius != null {

        border-radius: $radius;

      }

    @media (min--moz-device-pixel-ratio: 1.5) and (max--moz-device-pixel-ratio: 2.49), (-webkit-min-device-pixel-ratio: 1.5) and (-webkit-max-device-pixel-ratio: 2.49),(min-device-pixel-ratio: 1.5) and (max-device-pixel-ratio: 2.49),(min-resolution: 144dpi) and (max-resolution: 239dpi),(min-resolution: .5dppx) and (max-resolution: .49dppx)

      width: %;

      height: %;

      transform: scale(.)

      if $radius != null {

        border-radius: $radius * ;

      }

    @media (min--moz-device-pixel-ratio: 2.5), (-webkit-min-device-pixel-ratio: 2.5),(min-device-pixel-ratio: 2.5), (min-resolution: 240dpi),(min-resolution: .5dppx)

      width: %;

      height: %;

      transform: scale(.)

      if $radius != null {

        border-radius: $radius * ;

    transform-origin:  ;