关于无缝轮播图的一些思路

关键思路：复制第一张图片放到ul的最后，然后当图片切换到倒数第二张的时候直接切换新加的那张图片，再次从第一张切换到第二张的时候先瞬间切换到第一张图片，然后滑动到第二张。

实现代码如下

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<style>
    *{
        padding: 0;
        margin: 0;
    }
    .box{
        width: 500px;
        height: 200px;
        overflow: hidden;
        margin: 50px auto;

    }
    .inner{
        width: 500px;
        height: 200px;
        position: relative;

    }
    .inner ul{
        width: 600%;
        list-style: none;
        display: inline-block;
        position: absolute;
    }
    li{
        float: left;
    }
    .inner ol{
        list-style: none;
        display: inline-block;
        position: absolute;
        right: 50px;
        bottom: 20px;
    }
    .inner ol li{
        width: 20px;
        height: 20px;
        background-color: #cf00ff;
        margin: 0 5px;
        text-align: center;
        line-height: 20px;
        border: 1px solid #bcff9f;
        cursor: pointer;
    }
    .selected {
        background-color: #F14400!important;
    }
</style>
<body>
<div id="box" class="box">
    <div id="inner" class="inner">
        <ul>
            <li><img src="images/1.jpg" alt=""></li>
            <li><img src="images/2.jpg" alt=""></li>
            <li><img src="images/3.jpg" alt=""></li>
            <li><img src="images/4.jpg" alt=""></li>
            <li><img src="images/5.jpg" alt=""></li>
        </ul>
        <ol></ol>
        <div>
            <span></span>
            <span></span>
        </div>
    </div>
</div>
<script>
    var box = document.getElementById('box');
    var inner = box.firstElementChild||box.firstChild;
    var ul = inner.firstElementChild||box.firstChild;
    var uliArr = ul.children;
    var ol = inner.children[1];
    var spanArr = ol.parentNode.children[2].children;

    //************无缝轮播给ul最后添加第一张图
    //思路：赋值第一张图片放到ul的最后，然后当图片切换到第五张的时候
    //     直接切换第六章，再次从第一张切换到第二张的时候先瞬间切换到
    //     第一张图片，然后滑动到第二张
    newul = ul.children[0].cloneNode(true);
    ul.appendChild(newul);

    //************给ol添加内容
    for (var i=0;i<uliArr.length-1;i++) {
        var newLi = document.createElement("li");
        newLi.innerHTML = i+1;
        ol.appendChild(newLi);
    }
    ol.children[0].className = ol.children[0].className + " selected";
    //************给每个ol中的li绑定事件
    var oliArr = ol.children;
    for (var i=0;i<oliArr.length;i++) {
        oliArr[i].index = i;
        oliArr[i].onclick = function(){
            key = this.index;
            square = this.index;
            carousel(ul,500*this.index);
            for (var i=0;i<oliArr.length;i++){
                oliArr[i].className = oliArr[i].className.replace(/\s?selected/,"");
            }
            console.log(square);
            oliArr[square].className = oliArr[square].className+" selected";

        };
    }

    inner.onmouseover = function () {
        clearInterval(timer)
    }
    inner.onmouseout = function () {
        timer = setInterval(autoPlay,1000)
    }

    //************轮播函数
    function carousel(ele,distance) {
        clearInterval(ele.timer);
        ele.timer = setInterval(
            function () {
                speed =distance- Math.abs(ele.offsetLeft)>0?-10:10;
                console.log(distance- Math.abs(ele.offsetLeft));
                if (Math.abs(distance - Math.abs(ele.offsetLeft))<Math.abs(speed)){
                   clearInterval(ele.timer)
                }else {
                    ele.style.left = ele.offsetLeft + speed  + "px";
                    console.log(ele.style.left )
                }
        },10)

    }

    //************自动播放function
    var key = 0;//轮播图的运动值
    var square = 0;//方块运动的值
    timer = setInterval(autoPlay,1000) ;

    function autoPlay() {
        key++;
        if (key > uliArr.length-1){
            ul.style.left = 0;
            key=1;
        }
        square++;
        if (square>uliArr.length-2  ){
            square = 0;
        }
        carousel(ul,key*500);
        for (var i=0;i<oliArr.length;i++){
            oliArr[i].className = oliArr[i].className.replace(/\s?selected/,"");
        }
        console.log(square);
        oliArr[square].className = oliArr[square].className+" selected";
    }
</script>
</body>
</html>