JavaScript 实现纵向轮播图（初级版）

/*
* 工厂模式
* */
 
var Method=(function () {
  return {
    loadImage:function (arr,callback) {
      var img=new Image();
      img.arr=arr;
      img.list=[];
      img.num=0;
      img.callback=callback;
//      如果DOM对象下的事件侦听没有被删除掉，将会常驻堆中
//      一旦触发了这个事件需要的条件，就会继续执行事件函数
      img.addEventListener("load",this.loadHandler);
      img.self=this;
      img.src=arr[img.num];
    },
 
    loadHandler:function (e) {
      this.list.push(this.cloneNode(false));
      this.num++;
      if(this.num>this.arr.length-1){
        this.removeEventListener("load",this.self.loadHandler);
        this.callback(this.list);
        return;
      }
      this.src=this.arr[this.num];
    },
 
    $c:function (type,parent,style) {
      var elem=document.createElement(type);
      if(parent) parent.appendChild(elem);
      for(var key in style){
        elem.style[key]=style[key];
      }
      return elem;
    }
  }
})();

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
  <style>
    #con,#bgImg,#bgImg img
    {
      width: 100%;
      height: 500px;
    }
    #con
    {
      position: relative;
      margin: auto;
    }
    #bgImg{
      position: absolute;
    }
    #bgImg img{
      opacity: 1;
      transition: all 1s;
      position: absolute;
      left:0;
      top:0;
    }
    #iconImg
    {
      position: absolute;
      width: 120px;
      right: 50px;
      top:30px;
    }
    #iconImg img
    {
      margin-top: 8px;
      border: 2px solid #FFA50000;
      transition: all 0.5s;
    }
  </style>
  <script src="js/Method.js"></script>
</head>
<body>
  <div id="con">
    <div id="bgImg">
      <img src="img/a.jpeg">
    </div>
    <div id="iconImg">
      <img src="img/icon_a.jpeg">
      <img src="img/icon_b.jpeg">
      <img src="img/icon_c.jpeg">
      <img src="img/icon_d.jpeg">
      <img src="img/icon_e.jpeg">
    </div>
  </div>
  <script>
    var bgImg,iconImg,prevImg,imgList;//定义大图 小图的盒子(5个img)
    var N=0;//图像标记
    var arr=["img/a.jpeg","img/b.jpeg","img/c.jpeg","img/d.jpeg","img/e.jpeg"];//图片设置为数组形式 传参
    init();
    function init() {
      Method.loadImage(arr,loadFinishHandler)//预加载
    }
    function loadFinishHandler(list) {//预加载赋值
      imgList=list;
      bgImg=document.getElementById("bgImg");
      iconImg=document.getElementById("iconImg");
      for(var i=0;i<iconImg.children.length;i++){
        iconImg.children[i].num=i;
        iconImg.children[i].addEventListener("click",clickHandler);
      }
      changeBorder(iconImg.firstElementChild);
    }
    setInterval(autoImg,3000);
 
    function autoImg() {//自动轮播效果
      N++;  //全局变量 用于控制当前轮播顺序
      if (N>4) N=0;
      changeImg(N);//大图轮播
      changeBorder(iconImg.children[N]);//小图外边框轮播 设置第几个 弄懂参数代表含义
    }
    function clickHandler(e) {
      e =e || window.event;
      changeBorder(this);
      N=this.num;
      changeImg(this.num);
    }
    
    function changeBorder(elem) {
      if(prevImg){
        prevImg.style.border="2px solid #FFA50000";
      }
      prevImg=elem;
      prevImg.style.border="2px solid #FFA500";
    }
 
    function changeImg(index) {
      if(bgImg.children.length>1){
        bgImg.lastElementChild.remove();
      }
      bgImg.lastElementChild.style.opacity="0";
      imgList[index].style.opacity="1";
      bgImg.insertBefore(imgList[index],bgImg.firstElementChild);
    }
  </script>
</body>
</html>