<div class="ph-nav" data-pdt-block="pheader-n">
      <div class="ph-nav_shadow" style="left: 0px; width: 62px;"></div>
      <ul>
        <li class="ph-nav_item ph-nav_item--current">
          <a href="/" rel="external nofollow" >
          首页
          
          </a>
        </li>
        <li class="ph-nav_item">
          <a href="/all" rel="external nofollow" >
          全部
          </a>
        </li>
        ...
      </ul>
</div>

 <header>
    <div class="w">
      <div class="header_logo l"><img src="/UploadFiles/2021-04-02/logo.png">

编写css代码


.header_nav{
  width: 592px;
  height: 50px;
  position: relative;
}
.header_nav_shadow{
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  width: 72px;
  background: #F29400;
  transition: all ease-in-out .3s;
  z-index: 1;
}
.header_nav ul li{
  display: block;
  float: left;
  overflow: hidden;
  height: 50px;
  line-height: 50px;
  transition: all ease-in-out .3s;
  position: relative;
  z-index: 2;
}
.header_nav_li-hover a{
  color: #fff;
}
.header_nav ul li a{
  display: block;
  padding: 0 20px;
  height: 50px;
  line-height: 50px;
  transition: all ease-in-out .3s;
}


编写js代码（主要）


$(document).ready(function() { 
  $(".header_nav ul li").hover(function() { 

    var change = getLiData($(this));
    $(".header_nav_shadow").css('left',change[0]).width(change[1]);
    $(".header_nav ul").children("li:first-child").removeClass("header_nav_li-hover"); 
    $(this).addClass("header_nav_li-hover"); 
  }, function() { 
    $(".header_nav_shadow").css('left',0).width('72');
    $(this).removeClass("header_nav_li-hover"); 
    $(".header_nav ul").children("li:first-child").addClass("header_nav_li-hover");
  }); 
});
// 根据this li 获取需要改变的长度和偏移量
function getLiData(li){
  var left = 0;
  for(let i=0;i<li.index();i++){
    left+=$(".header_nav ul li:eq("+i+")").width();
  }
  var change=[left,li.width()];
  return change;
}