border.css

该 css 样式用于解决移动端 1 像素边框问题。问题分析：有些手机的屏幕分辨率较高，是 2-3 倍屏幕。css 样式中 border:1px solid red;在 2 倍屏下，显示的并不是 1 个物理像素，而是 2 个物理像素。为了解决这个问题，引入 border.css 是非常有必要的。

具体代码

@charset "utf-8";
.border,
.border-top,
.border-right,
.border-bottom,
.border-left,
.border-topbottom,
.border-rightleft,
.border-topleft,
.border-rightbottom,
.border-topright,
.border-bottomleft {
  position: relative;
}
.border::before,
.border-top::before,
.border-right::before,
.border-bottom::before,
.border-left::before,
.border-topbottom::before,
.border-topbottom::after,
.border-rightleft::before,
.border-rightleft::after,
.border-topleft::before,
.border-topleft::after,
.border-rightbottom::before,
.border-rightbottom::after,
.border-topright::before,
.border-topright::after,
.border-bottomleft::before,
.border-bottomleft::after {
  content: '\0020';
  overflow: hidden;
  position: absolute;
}
/* border
 * 因，边框是由伪元素区域遮盖在父级
 * 故，子级若有交互，需要对子级设置
 * 定位 及 z轴
 */
.border::before {
  box-sizing: border-box;
  top: 0;
  left: 0;
  height: 100%;
  width: 100%;
  border: 1px solid #eaeaea;
  transform-origin: 0 0;
}
.border-top::before,
.border-bottom::before,
.border-topbottom::before,
.border-topbottom::after,
.border-topleft::before,
.border-rightbottom::after,
.border-topright::before,
.border-bottomleft::before {
  left: 0;
  width: 100%;
  height: 1px;
}
.border-right::before,
.border-left::before,
.border-rightleft::before,
.border-rightleft::after,
.border-topleft::after,
.border-rightbottom::before,
.border-topright::after,
.border-bottomleft::after {
  top: 0;
  width: 1px;
  height: 100%;
}
.border-top::before,
.border-topbottom::before,
.border-topleft::before,
.border-topright::before {
  border-top: 1px solid #eaeaea;
  transform-origin: 0 0;
}
.border-right::before,
.border-rightbottom::before,
.border-rightleft::before,
.border-topright::after {
  border-right: 1px solid #eaeaea;
  transform-origin: 100% 0;
}
.border-bottom::before,
.border-topbottom::after,
.border-rightbottom::after,
.border-bottomleft::before {
  border-bottom: 1px solid #eaeaea;
  transform-origin: 0 100%;
}
.border-left::before,
.border-topleft::after,
.border-rightleft::after,
.border-bottomleft::after {
  border-left: 1px solid #eaeaea;
  transform-origin: 0 0;
}
.border-top::before,
.border-topbottom::before,
.border-topleft::before,
.border-topright::before {
  top: 0;
}
.border-right::before,
.border-rightleft::after,
.border-rightbottom::before,
.border-topright::after {
  right: 0;
}
.border-bottom::before,
.border-topbottom::after,
.border-rightbottom::after,
.border-bottomleft::after {
  bottom: 0;
}
.border-left::before,
.border-rightleft::before,
.border-topleft::after,
.border-bottomleft::before {
  left: 0;
}
@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: 1.49dppx) {
  /* 默认值，无需重置 */
}
@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: 1.5dppx) and (max-resolution: 2.49dppx) {
  .border::before {
    width: 200%;
    height: 200%;
    transform: scale(0.5);
  }
  .border-top::before,
  .border-bottom::before,
  .border-topbottom::before,
  .border-topbottom::after,
  .border-topleft::before,
  .border-rightbottom::after,
  .border-topright::before,
  .border-bottomleft::before {
    transform: scaleY(0.5);
  }
  .border-right::before,
  .border-left::before,
  .border-rightleft::before,
  .border-rightleft::after,
  .border-topleft::after,
  .border-rightbottom::before,
  .border-topright::after,
  .border-bottomleft::after {
    transform: scaleX(0.5);
  }
}
@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: 2.5dppx) {
  .border::before {
    width: 300%;
    height: 300%;
    transform: scale(0.33333);
  }
  .border-top::before,
  .border-bottom::before,
  .border-topbottom::before,
  .border-topbottom::after,
  .border-topleft::before,
  .border-rightbottom::after,
  .border-topright::before,
  .border-bottomleft::before {
    transform: scaleY(0.33333);
  }
  .border-right::before,
  .border-left::before,
  .border-rightleft::before,
  .border-rightleft::after,
  .border-topleft::after,
  .border-rightbottom::before,
  .border-topright::after,
  .border-bottomleft::after {
    transform: scaleX(0.33333);
  }
}