JavaScript实现移动端带transition动画的轮播效果

<div id="box">
 <ul id="lilist">
 <li><img src="5.jpg" alt=""></li>
 <li><img src="1.jpg" alt=""></li>
 <li><img src="2.jpg" alt=""></li>
 <li><img src="3.jpg" alt=""></li>
 <li><img src="4.jpg" alt=""></li>
 <li><img src="5.jpg" alt=""></li>
 <li><img src="1.jpg" alt=""></li>
 </ul>
 <ul id="items">
 <li class="active"></li>
 <li></li>
 <li></li>
 <li></li>
 <li></li>
 </ul>
</div>

 *{ margin: 0;padding: 0; }
 html,body{ height: 100%;}
 #box{
  width: 100%;
  overflow: hidden;
  position: relative;
 }
 #box #lilist{
  /* 宽度根据子元素个数动态确定 */
  /*width: 500%;*/
  position: relative;
  float: left;
  white-space: nowrap;
  list-style: none;
  overflow: hidden;
 }
 #box #lilist li{
  float: left;
  height: 200px;
 }
 #box #lilist li img{
  display: block;
  width: 100%;
  height: 100%;
  object-fit: fill;
 }

 #box #items{
  position: absolute;
  list-style: none;
  width: 30%;
  bottom: 10px;
  left: 35%;
  display: flex;
  flex-flow: row nowrap;
  justify-content: space-between;
 }
 #box #items li{
  float: left;
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background-color: black;
 }
 #box #items .active{
  background-color: red;
 }

window.onload = function(){
var totalli1 = document.querySelectorAll("#box>#lilist>li");
 var totalli2 = document.querySelectorAll("#box>#items>li");

 // 动态改变轮播图宽度
 changewidth();
 function changewidth(){
 var newstyle = document.createElement("style");
 var mycss = "#lilist{ width : "+totalli1.length+"00% }";
  mycss += "#lilist li{ width : "+(100/totalli1.length)+"% }"
 newstyle.innerHTML = mycss;
 document.head.appendChild(newstyle);
 }

 var getbox = document.getElementById("box");
 var getlist = document.getElementById("lilist");
 var startx = 0, endx = 0, disx = 0;
 var listleft = 0, finalx = 0;
 var windowx = document.documentElement.offsetWidth;
 var listx = getlist.offsetWidth;
 var moveindex = 0;
 // 自动轮播控制变量
 var num = 1, index = 0;
 // 先让他左滑
 transforms(getlist,"translateX",-windowx);

 getbox.addEventListener("touchstart",function(event){
 let touch = event.changedTouches[0];
 startx = touch.clientX;
 // 首位位置判断，并重新定位.鼠标刚放上去就要改变位置，不然move移动再改的话会和移动的transform冲突，也不能在鼠标离开时切换，会影响到移动的滑动效果。这个过程中是瞬间完成的，不允许过渡或动画，显得平滑。
 let lastx = Math.round(-transforms(getlist,"translateX")/windowx);
 if(lastx<1){
  lastx = totalli1.length-2;
 }else if(lastx>totalli1.length-2){
  lastx = 1;
 }
 // 移动到指定位置
 transforms(getlist,"translateX",-lastx*windowx);
 // 给 listleft 赋值
 listleft = transforms(getlist,"translateX");
 // 清除过度缓冲
 getlist.style.transition = "none";
 // 清除计时器
 window.clearInterval(timer);
 })
 getbox.addEventListener("touchmove",function(event){
 let touch = event.changedTouches[0];
 endx = touch.clientX;
 disx = endx - startx;
 finalx = disx+listleft;

 transforms(getlist,"translateX",finalx)
 })
 getbox.addEventListener("touchend",function(event){
 let touch = event.changedTouches[0];
 // 滑动的屏宽个数。
 let lastx = 0;
 // ul 距屏幕左侧的距离与屏宽的比例
 lastx = Math.round(-transforms(getlist,"translateX")/windowx);
 if(lastx<=0){
  lastx = 0;
 }else if(lastx>totalli1.length-1){
  lastx = totalli1.length-1;
 }
 transforms(getlist,"translateX",-lastx*windowx);
 getlist.style.transition = "transform 0.3s";
 // 下部红点跟随,获取下标。诸位请注意下面几个数字的含义，4,5,6的意思你们自己思考一下
 moveindex = lastx-1;
 if(lastx==1||lastx==6){
  moveindex = 0;
 }else if(lastx==0||lastx==5){
  moveindex = 4;
 }
 movecircle(moveindex);
 // 重新添加计时器，自动轮播
 timer = window.setInterval(playself,3000);
 // 改变num和index的值,以确定计时器开始位置
 console.log(moveindex+"。。。"+lastx)
 index = moveindex;
 num = lastx;
 })
 // 自动轮播
 var timer = window.setInterval(playself,3000);
 function playself(){
 // 清除过渡残留
 getlist.style.transition = "none";
 if(num==totalli1.length-1){
  transforms(getlist,"translateX",-windowx);
  num = 1;
 }
 // 再添加一个一次性计时器即可分开与 interval 的冲突
 setTimeout(function(){
  transforms(getlist,"translateX",-windowx*(++num));
  getlist.style.transition = "transform 0.5s";
  // 原点跟随移动
  index++;
  if(index==totalli2.length){
  index = 0;
  totalli2[index].classList.add("active");
  }
  movecircle(index);
 },1)
 }
 // 红点移动函数
 function movecircle(getindex){
 for(let i=0;i<totalli2.length;i++){
  totalli2[i].classList.remove("active");
  if(getindex==i){
  totalli2[getindex].classList.add("active");
  }
 }
 }
}