使用Javascript开发sliding-nav带滑动条效果的导航插件

<script src="/path/to/sliding-nav.js"></script>
<ul class="nav sliding-nav" sn-color="#F00" sn-radius="0px" sn-height="3px">
 <li class="active">菜单项1</li>
 <li>菜单项2</li>
 <li>菜单项3</li>
<ul>

function init() {
 
 var navs = document.getElementsByClassName('sliding-nav');
 
 for (var i = 0; i < navs.length; i++) {
 
 
  //创建一个DIV与当前导航竖向对齐
  var indi = document.createElement("div");
  indi.id = "slna-indicator"
 
  indi.style.borderRadius = navs[i].getAttribute("sn-radius") || "0px"
  indi.style.height = navs[i].getAttribute("sn-height") || "3px"
  indi.style.backgroundColor = navs[i].getAttribute("sn-color") || "#F00"
 
  indi.style.position = "absolute"
  indi.style.transition = "0.5s"
 
  //查找当前子菜单项,如果有类名active或者是selected就视为当前项，如果没有使用第1项
  var selected = navs[i].getElementsByClassName('active')
  if (selected.length == 0) {
   selected = navs[i].getElementsByClassName('selected')
  }
  if (selected.length == 0) {
   selected = navs[i].children
  }
 
  if (selected.length == 0) {
   throw Error('Sorry, Navigation bar has no item at all!');
  }
 
  selected = selected[0];
 
  indi.style.width = selected.offsetWidth + "px";
  indi.style.top = selected.offsetHeight + "px";
  indi.style.left = selected.offsetLeft + "px";
  navs[i].parentElement.insertBefore(indi, navs[i]);
 
  //未完成，下面插入代码以绑定事件
 
 }
 
}

for (var j = 0; j < navs[i].children.length; j++) {

   hover(navs[i].children[j], function(e, elem) {

    indi.style.width = elem.offsetWidth + "px";
    indi.style.left = elem.offsetLeft + "px";

   });

   //移出导航就恢复默认
   hover(navs[i], null, function(e, elem) {
    indi.style.width = selected.offsetWidth + "px";
    indi.style.left = selected.offsetLeft + "px";
   });

  }

for (var j = 0; j < navs[i].children.length; j++) {

   hover(navs[i].children[j], function(e, elem) {

    indi.style.width = elem.offsetWidth + "px";
    indi.style.left = elem.offsetLeft + "px";

   });

   //移出导航就恢复默认
   hover(navs[i], null, function(e, elem) {
    indi.style.width = selected.offsetWidth + "px";
    indi.style.left = selected.offsetLeft + "px";
   });

  }