JS实现京东商品分类侧边栏

<div>
  <img src="/1.png" alt="">
 </div>
 <ul>
  <li><a href="">京东秒杀</a></li>
  <li class="two"><a href="">欢迎</a></li>
  <li><a href="">特色优选</a></li>
  <li><a href="">频道广场</a></li>
  <li><a href="">为你推荐</a></li>
  <li class="two"><a href="">客服</a></li>
  <li style="border-bottom: none;" class="two"><a href="">反馈</a></li>
</ul>

<style>
   {
   margin: 0;
   padding: 0;
  }

  a {
   text-decoration: none;
   color: #000;
  }

  div {
   width: 100%;

  }

  img {
   margin-left: 300px;
   display: block;
   margin: 0 auto;
  }

  ul {
   position: absolute;
   display: none;
   : 350px;
   left: 1700px;
   width: 60px;
   height: 400px;
   border: 1px solid red;
   box-sizing: border-box;

  }

  ul li {
   width: 100%;
   height: 57px;
   list-style: none;
   text-align: center;
   float: right;
   padding: 5px 10px;
   line-height: 26px;
   text-align: center;
   float: left;
   box-sizing: border-box;
   border-bottom: 1px solid #eee;
  }

  li:hover {
   background-color: red;
  }

  li:hover a {
   color: white;
  }

  .two {
   line-height: 52px;
  }

<script>
  document.addEventListener('scroll', function () {
   var ul = document.querySelector('ul')
   console.log(window.pageYOffset)
   if (window.pageYOffset > 700) {
    ul.style.display = 'block'
    ul.style.position = 'fixed';
   } else {
    ul.style.display = 'none'
   }
  })
</script>