JS实现首尾无缝衔接的图片轮播功能

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head>
 <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
 <title>图片轮播</title>
 <style type="text/css">
 body,div,ul,li,a,img{margin: 0;padding: 0;}
 ul,li{list-style: none;}
 a{text-decoration: none;}
 #wrapper{
  position: relative;
  margin: 30px auto; /* 上下边距30px，水平居中 */
  width: 400px;
  height: 200px;
 }
 #banner{
  position:relative;
  width: 400px;
  height: 200px;
  overflow: hidden;
 }
 .imgList{
  position:relative;
  width:2000px;
  height:200px;
  z-index: 10;
  overflow: hidden;
 }
 .imgList li{float:left;display: inline;}
 #prev,
 #next{
  position: absolute;
  top:80px;
  z-index: 20;
  cursor: pointer;
  opacity: 0.2;
  filter:alpha(opacity=20);
 }
 #prev{left: 10px;}
 #next{right: 10px;}
 #prev:hover,
 #next:hover{opacity: 0.5;filter:alpha(opacity=50);}

</style>
</head>
<body>
 <div id="wrapper"><!-- 最外层部分 -->
 <div id="banner"><!-- 轮播部分 -->
  <ul class="imgList"><!-- 图片部分 -->
  <li><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="./img/1.jpg" width="400px" height="200px" alt="1"></a></li>
  <li><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="./img/2.jpg" width="400px" height="200px" alt="2"></a></li>
  <li><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="./img/3.jpg" width="400px" height="200px" alt="3"></a></li>
  <li><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="./img/4.jpg" width="400px" height="200px" alt="4"></a></li>
  <li><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="./img/5.jpg" width="400px" height="200px" alt="5"></a></li>
 </ul>
 <img src="./img/prev.png" width="40px" height="40px" id="prev">
 <img src="./img/next.png" width="40px" height="40px" id="next">
</div>
</div>
<script type="text/javascript" src="./js/jquery-3.2.1.min.js"></script>
<script type="text/javascript">
var curIndex = 0, //当前index
 imgLen = $(".imgList li").length; //图片总数
$(".imgList").css("width", (imgLen+1)*400+"px");
// 定时器自动变换3秒每次
var autoChange = setInterval(function(){
 if(curIndex < imgLen-1){
  curIndex ++;
 }else{
  curIndex = 0;
 }
 //调用变换处理函数
 changeTo(curIndex);
},3000);

//左箭头滑入滑出事件处理
$("#prev").hover(function(){
 //滑入清除定时器
 clearInterval(autoChange);
}, function(){
 //滑出则重置定时器
 autoChangeAgain();
});

//左箭头点击处理
$("#prev").click(function(){
 //根据curIndex进行上一个图片处理
 // curIndex = (curIndex > 0) ? (--curIndex) : (imgLen - 1);
 if (curIndex == 0) {
  var element = document.createElement("li");
  element.innerHTML = $(".imgList li")[imgLen - 1].innerHTML;
  // $(".imgList li")[imgLen - 1].remove();
  $(".imgList").prepend(element);
  $(".imgList").css("left", -1*400+"px");
  changeTo(curIndex);
  curIndex = -1;
 } else if (curIndex == -1) {
  $(".imgList").css("left", -(imgLen-1)*400+"px");
  curIndex = imgLen-2;
  $(".imgList li")[0].remove();
  changeTo(curIndex);
 } else {
  --curIndex;
  changeTo(curIndex);
 }

});

//右箭头滑入滑出事件处理
$("#next").hover(function(){
 //滑入清除定时器
 clearInterval(autoChange);
}, function(){
 //滑出则重置定时器
 autoChangeAgain();
});
//右箭头点击处理
$("#next").click(function(){
 // curIndex = (curIndex < imgLen - 1) ? (++curIndex) : 0;
 console.log(imgLen);
 if (curIndex == imgLen-1) {
  var element = document.createElement("li");
  element.innerHTML = $(".imgList li")[0].innerHTML;
  // $(".imgList li")[0].remove();
  $(".imgList").append(element);
  ++curIndex;
 } else if (curIndex == imgLen) {
  curIndex = 0;
  $(".imgList").css("left", "0px");
  $(".imgList li")[imgLen].remove();
  curIndex++;
 } else {
  ++curIndex;
 }
 changeTo(curIndex);
});

//清除定时器时候的重置定时器--封装
function autoChangeAgain(){
 autoChange = setInterval(function(){
  if(curIndex < imgLen-1){
   curIndex ++;
  }else{
   curIndex = 0;
  }
 //调用变换处理函数
 changeTo(curIndex);
 },3000);
}


function changeTo(num){
 var goLeft = num * 400;
 $(".imgList").animate({left: "-" + goLeft + "px"},500);
}
</script>
</body>
</html>