7.边框问题解决方法以及reset的使用

1px边框问题在实际项目中非常重要

一、关于reset.css

因为不同的浏览器默认的样式不同，所以在着手项目开始前，我们需要引入reset.css，将所有html标签的默认样式统一化。我这里推荐一个下载reset.css的网站：https://cssreset.com/，里面还有一些normalize.css之类的，大家有兴趣可以研究。

二、关于1px边框问题

因为自从retina屏以来，不同的手机又不同的像素密度，css中的1px并不等于移动设备中的1px， 最直接的表现就是1px边框问题；简单说就是你给border的css写个1px，到手机上却变粗了显示成2px。
所以在项目中我们引入一个border.css解决这个问题。

三、项目中引入

1、新建styles文件夹
把reset.css和border.css粘贴到此：

reset.css

@charset "utf-8";html{background-color:#fff;color:#000;font-size:12px}
body,ul,ol,dl,dd,h1,h2,h3,h4,h5,h6,figure,form,fieldset,legend,input,textarea,button,p,blockquote,th,td,pre,xmp{margin:0;padding:0}
body,input,textarea,button,select,pre,xmp,tt,code,kbd,samp{line-height:1.5;font-family:tahoma,arial,"Hiragino Sans GB",simsun,sans-serif}
h1,h2,h3,h4,h5,h6,small,big,input,textarea,button,select{font-size:100%}
h1,h2,h3,h4,h5,h6{font-family:tahoma,arial,"Hiragino Sans GB","微软雅黑",simsun,sans-serif}
h1,h2,h3,h4,h5,h6,b,strong{font-weight:normal}
address,cite,dfn,em,i,optgroup,var{font-style:normal}
table{border-collapse:collapse;border-spacing:0;text-align:left}
caption,th{text-align:inherit}
ul,ol,menu{list-style:none}
fieldset,img{border:0}
img,object,input,textarea,button,select{vertical-align:middle}
article,aside,footer,header,section,nav,figure,figcaption,hgroup,details,menu{display:block}
audio,canvas,video{display:inline-block;*display:inline;*zoom:1}
blockquote:before,blockquote:after,q:before,q:after{content:"\0020"}
textarea{overflow:auto;resize:vertical}
input,textarea,button,select,a{outline:0 none;border: none;}
button::-moz-focus-inner,input::-moz-focus-inner{padding:0;border:0}
mark{background-color:transparent}
a,ins,s,u,del{text-decoration:none}
sup,sub{vertical-align:baseline}
html {overflow-x: hidden;height: 100%;font-size: 50px;-webkit-tap-highlight-color: transparent;}
body {font-family: Arial, "Microsoft Yahei", "Helvetica Neue", Helvetica, sans-serif;color: #333;font-size: .28em;line-height: 1;-webkit-text-size-adjust: none;}
hr {height: .02rem;margin: .1rem 0;border: medium none;border-top: .02rem solid #cacaca;}
a {color: #25a4bb;text-decoration: none;}

border.css

@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(.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(.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(.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(.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(.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(.33333);
  }
}

2、main.js中引入reset.css以及border.css

3、配置路径
我觉得'./assets/styles/reset.css'这个路径太长了，所以我们在webapck.base.conf.js中的alias中配置下路径

4、main.js中简化下路径引入

上面步骤完成以后，因为修改了webpack里面的配置，所以我们需要npm run dev重启一下服务，ok。