css3实现菜单栏选中时的过渡效果

（如有错敬请指点，以下是我工作中遇到并且解决的问题）

效果图：

点击后的效果：

可以通过 https://littlehiuman.github.io/07-menus/index-2.html 查看效果。

https://github.com/littleHiuman/littleHiuman.github.io 求点star~~~

HTML:

<ul class="menus">
  <li class="active">菜单1</li>
  <li>菜单2</li>
  <li>菜单3</li>
  <li>菜单4</li>
  <li>菜单5</li>
  <li>菜单6</li>
  <li class="bar"><i class="active_bg"></i></li>
</ul>

CSS:

* {
  margin: 0;
  padding: 0;
  list-style: none;
}

ul {
  height: 40px;
  position: relative;
  line-height: 44px;
}

ul li {
  width: 16.66666%;
  height: 100%;
  float: left;
  color: #999;
  text-align: center;
  cursor: pointer;
}

ul .bar {
  width: 16.66666%;
  height: 3px;
  line-height: 0;
  position: absolute;
  left: 0;
  bottom: 1px;
  transform: translateX(0%);
  transition: 0.2s linear;
  -webkit-transition: 0.2s linear;
}

ul .bar i {
  width: 70%;
  height: 3px;
  display: inline-block;
}

.active {
  color: darkgreen;
}

.active_bg {
  background-color: darkgreen;
}

JAVASCRIPT:

var menus = document.querySelector('.menus');
var children = menus.children;
for (var i = 0; i < children.length; i++) {
  children[i]['data-index'] = i;
}
menus.onclick = function (event) {
  event = event || window.event;
  if (event.target.tagName === 'LI') {
    for (var i = 0; i < children.length; i++) {
      children[i].className = children[i].className.replace(/active/, '')
    }
    event.target.className += ' active';
    children[children.length - 1].style['-webkit-transform'] = 'translateX(' + (event.target['data-index'] * 100) + '%)'
  }
}