Realization of millet carousel map by JS

Native JS imitation millet carousel map (the latest version is easy to understand), for your reference, the specific contents are as follows

The main achievable effects of this content:

Automatic carousel You can click on the top one and the bottom one to switch pictures Click on the small dot at the bottom right to switch pictures

Code section:

H5:

<div class="wrap">
    <ul class="list">
      <li class="item active"><img src="img/001.jpg" alt=""></li>
      <li class="item"><img src="img/002.jpg"" alt=""></li>
      <li class="item"><img src="img/001.jpg" alt=""></li>
      <li class="item"><img src="img/002.jpg" alt=""></li>
      <li class="item"><img src="img/001.jpg" alt=""></li>
    </ul>
    <!--  Small dot  -->
    <ul class="pointList">
      <li class="point active" data-index="0"></li>
      <li class="point" data-index="1"></li>
      <li class="point"data-index="2"></li>
      <li class="point"data-index="3"></li>
      <li class="point"data-index="4"></li>
    </ul>
    <button type="button" class="btn" id="goPre"><</button>
    <button type="button" class="btn" id="goNext">></button>
</div>

CSS section:

<style>
    .wrap {
      width: 800px;
      height: 400px;
      position: relative;
    }

    .list {
      width: 800px;
      height: 400px;
      list-style: none;
      position: relative;
      padding-left: 0px;
    }

    .item {
      position: absolute;
      width: 100%;
      height: 100%;
      color: white;
      font-size: 50px;
      opacity: 0.6;
      transform: all .8s;
    }
    .item img{
      width: 800px;
      height: 400px;
    }
    .btn {
      width: 50px;
      height: 100px;
      position: absolute;
      top: 150px;
      z-index: 100;
    }

    #goPre {
      left: 0px;
    }

    #goNext {
      right: 0px;
    }

    .item.active {
      opacity: 1;
      z-index: 10;
    }

    .pointList{
      padding-left: 0;
      list-style: none;
      position: absolute;
      right: 20px;
      bottom: 20px;
      z-index: 1000;
    }
    .point{
      width: 10px;
      height: 10px;
      background-color: rgba(0,0,0,0.4);
      border-radius: 50%;
      float: left;
      margin-right: 16px;
      border-style: solid;
      border-width: 2px;
      border-color: rgba(255,255,255, 0.6);
      cursor: pointer;
    }
    .point.active{
      background-color: rgba(255,255,255,0.4);
    }
</style>

JS Part

<script>
    // Get Node 
    var items = document.getElementsByClassName('item')// Picture 
    var goPreBtn = document.getElementById('goPre');
    var goNextBtn = document.getElementById('goNext');
    // Acquisition point 
    var points=document.getElementsByClassName('point');

   var time=0;// Timer picture jump parameter 

    var index = 0; // Indicates which picture is on display 
    // What point can you show 

    var clearActive=function(){
      for(var i=0;i<items.length;i++){
        items[i].className='item';
        points[i].className='point';
      }
    }

    var goIndex=function(){
      clearActive();
      items[index].className='item active';
      points[index].className='point active';
    }

    var goNext=function(){
      if(index<4){
        index++;
      }else{
        index=0;
      }
      goIndex();
    }
    var goPre=function(){
      if(index==0){
        index=4;
      }else{
        index--;
      }
      goIndex();
    }

    // Click under 1 Zhang Switch Picture 
    goNextBtn.addEventListener('click' ,function(){
      goNext();
      time=0;
    })
  // Click on 1 Zhang carries out switching pictures 
    goPreBtn.addEventListener('click' ,function(){
      goPre();
      time=0;
    })

   for(var i=0;i<points.length;i++){
    points[i].addEventListener('click',function(){
      var pointIndex=this.getAttribute('data-index');
      index=pointIndex;
      goIndex();
      time=0;
    })
   }
   
  // Automatic carousel timer 
  setInterval(function(){
    time++;
    if(time==20){
      goNext();
      time=0;
    } 
  },100)
</script>