老师请您帮忙看一下代码谢谢

相关代码：

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
     *{
       padding:0px;
       margin:0px;
     }
     .box{
       width:650px;
       height:360px;
       margin:50px auto;
       border: 1px solid #000;
       position: relative;
     }
     .box ul{
       width:5000px;
       list-style: none;
       left:0px;
       position: relative;
       /* transition: left 1s ease 0s; */
     }
     .box ul li{
       float:left;
     }
     .leftbtn{
       width:30px;
       height:30px;
       background-color: red;
       border: 1px solid #000;
       text-decoration: none;
       border-radius: 50%;
       position: absolute;
       left:20px;
       top:50%;
       margin-top:-25px;
       font-size: 25px;
       color:white;
       text-align: center;
       line-height: 30px;
     }
     .rightbtn{
       width:30px;
       height:30px;
       background-color: red;
       border: 1px solid #000;
       text-decoration: none;
       border-radius: 50%;
       position: absolute;
       right:20px;
       top:50%;
       margin-top:-25px;
       font-size: 25px;
       color:white;
       text-align: center;
       line-height: 30px;
     }
  </style>
</head>
<body>
   <div class="box"id="box">
      <ul class="list"id="list">
        <li><img src="image/hudie.jpg"width="650px"height="360"></li>
        <li><img src="image/huoshaoyun.jpg"width="650px"height="360"></li>
        <li><img src="image/jiudian.jpg"width="650px"height="360"></li>
        <li><img src="image/shanshui.jpg"width="650px"height="360"></li>
        <li><img src="image/wangzixuan1.jpg"width="650px"height="360"></li>
      </ul>
      <a href="javascript:;"class="leftbtn"id="leftbtn">&lt</a>
      <a href="javascript:;"class="rightbtn"id="rightbtn">&gt</a>
   </div>
</body>
<script>
    var leftbtn=document.getElementById('leftbtn');
    var rightbtn=document.getElementById('rightbtn');
    var list=document.getElementById('list');
    //当前ul left的值
    var left=0;
</script>
</html>

老师我想请您帮忙检查一下代码，为什么我做的这个没有一丁点的效果

慕粉1924517932 2021-12-11

源自：DOM 1-1 课程简介