如何在css中为nav菜单设置border-left？

Question

这是我工作的jsfiddle:http://jsfiddle.net/nalinc/rym2zku1/9/

nav ul,
nav ol {
  list-style: none;
  margin: 0;
  padding: 0;
}
.nav-item ul {
  padding: inherit;
  border: 1px solid black;
  text-align: left;
  border-radius: 4px;
}
.nav-item ul li:hover {
  background-color: #d1d1d1;
}
.nav-bar {
  text-align: center;
}
@media screen and (min-width: 769px) {
  .nav-bar--left {
    display: table;
    table-layout: fixed;
    width: 100%;
    text-align: left;
  }
  .nav-bar--left .grid-item {
    float: none;
    display: table-cell;
    vertical-align: middle;
  }
}
#nav {
  position: relative;
  display: block;
  list-style-type: none;
  padding: 0;
  margin: 20px 0;
  font-family: "Raleway", "HelveticaNeue", "Helvetica Neue", sans-serif;
  white-space: nowrap;
}
.nav-bar--left #nav {
  margin: 1em 0 0;
  text-align: right;
}
@media screen and (max-width: 768px) {
  #nav,
  .nav-bar--left #nav {
    width: 100%;
    white-space: normal;
    margin: 20px 0 10px;
    text-align: inherit;
  }
}
.nav-item {
  position: relative;
  display: inline-block;
  padding: 2px 30px;
}
@media screen and (max-width: 768px) {
  .nav-item {
    padding: 10px 20px;
  }
}
#nav>.nav-item {
  border-left: 1px solid #e8e8e8;
}
#nav>.nav-item.first {
  border-left: none;
  padding-left: 0;
}
@media screen and (max-width: 768px) {
  #nav>.nav-item {
    border: 0 none;
  }
}
.nav-item-link {
  display: inline-block;
  color: #211f1f;
  font-size: 14px;
  zoom: 1;
  *display: inline;
}
.nav-item-link:hover {
  color: #333;
}
.nav-item-link .nav-item.active .nav-item-link {
  color: #333333;
}
.sub-nav .sub-nav {
  display: none !important;
}
.supports-no-csstransforms .sub-nav {
  white-space: normal;
  width: 200px;
  margin-left: -100px;
}
.sub-nav:before {
  content: '';
  display: block;
  position: absolute;
  top: 5px;
  right: 47%;
  border-left: 5px solid transparent;
  border-right: 5px solid transparent;
  border-bottom: 5px solid #211f1f;
  z-index: 40;
}
.sub-nav-item,
#moreMenu--list .nav-item {
  display: block;
  overflow: hidden;
  padding: 0;
  margin: 0;
  background-color: #211f1f;
}
.sub-nav-item.first,
#moreMenu--list .nav-item:first-child {
  border-top-left-radius: 4px;
  border-top-right-radius: 4px;
}
.sub-nav-item.last,
#moreMenu--list .nav-item:last-child {
  border-bottom-right-radius: 4px;
  border-bottom-left-radius: 4px;
}
.sub-nav-item-link,
#moreMenu--list .nav-item .nav-item-link {
  display: block;
  padding: 15px 20px;
  margin: 0;
  color: #ffffff;
  text-align: center;
  border-top: 1px solid #0b0a0a;
}
.sub-nav-item-link.first,
.sub-nav-item-link:first-child,
#moreMenu--list .nav-item .nav-item-link.first,
#moreMenu--list .nav-item .nav-item-link:first-child {
  border-top: none;
}
.sub-nav-item-link:hover,
.sub-nav-item-link:focus,
#moreMenu--list .nav-item .nav-item-link:hover,
#moreMenu--list .nav-item .nav-item-link:focus {
  color: #ffffff;
  border-top: 1px solid #0b0a0a;
  background-color: #0b0a0a;
}
.sub-nav-item-link:hover.first,
.sub-nav-item-link:hover:first-child,
.sub-nav-item-link:focus.first,
.sub-nav-item-link:focus:first-child,
#moreMenu--list .nav-item .nav-item-link:hover.first,
#moreMenu--list .nav-item .nav-item-link:hover:first-child,
#moreMenu--list .nav-item .nav-item-link:focus.first,
#moreMenu--list .nav-item .nav-item-link:focus:first-child {
  border-top: none;
}
#nav {
  border-top: 1px solid #ccc;
  border-bottom: 1px solid #ccc;
  text-align: center
}
#nav a {
  text-decoration: none;
  color: #666;
  display: inline-block;
  padding: 10px;
  font-size: 13px;
}
#nav ul {
  position: absolute;
  top: 100%;
  left: 0;
  text-align: left;
  width: 170px;
  border: 1px solid #ccc;
  display: none;
}
#nav li:hover ul {
  display: block;
}

<nav id="navWrap" role="navigation">
  <ul id="nav">
    <li class="nav-item first active">
      <a class="nav-item-link" href="/">Home</a>                
    </li>
    <li class="nav-item">
      <a class="nav-item-link" href="catalog.html">Catalog</a>  
      <ul>
        <li><a href="#">Data Listing</a></li>
        <li><a href="#">Web Scheduling</a></li>
        <li><a href="#">Google Maps Application</a></li>
      </ul>         
    </li>
    <li class="nav-item">
      <a class="nav-item-link" href="/blogs/news">Blog</a>                
    </li>
    <li class="nav-item">
      <a class="nav-item-link" href="/pages/about-us">About Us</a>                
    </li>
  </ul>
</nav>

现在我需要border-left为每个列表.

我需要这样的形象:

当我添加时border-left,它会被触及border-bottom.

#nav ul {
    position: absolute;
    top: 100%;
    left: 0;
    text-align: left;
    width: 170px;
    border: 1px solid #ccc;
    display: none;
}

任何人都可以帮我解决这个问题吗？提前致谢.

Answer 1

盒子阴影黑客!

演示:http://jsfiddle.net/rym2zku1/29/

额外的CSS

.nav-item:not(:last-child) {
    -webkit-box-shadow: 10px 0px 0px -9px red;
       -moz-box-shadow: 10px 0px 0px -9px red;
            box-shadow: 10px 0px 0px -9px red;
}

垂直条红色,以更好地突出解决方案

结果

说明

我们[ab]使用CSS box-shadow属性在元素周围绘制部分边框.nav-item.

CSS的"部分"可以描述如下:

1. 水平偏移我们想要阴影坐在右边多远？
2. 垂直偏移我们希望阴影坐到底部多远？
3. 模糊半径阴影想要的锐度是多少？
4. 传播半径阴影从其边缘扩散多远？
5. 颜色

这里的黑客是阴影向右移动10px,但是扩散(-9px)对此有效,以便再次有效地"拉回".这种扩散的减少发生在所有维度上,因此我们也从元素的全高度获得9px"回拉".