实现无缝切换可以多加两张图，在第一张前面加上最后一张图，在最后一张图后面加上第一张图。刚好之前写过一个，JS原生，具体代码如下：

html

轮播图

.wrap{

width: 900px;

height: 500px;

overflow: hidden;

margin: 0 auto;

margin-top: 50px;

position: relative;

}

.list{

position: absolute;

width: 5400px;

}

img{

width: 900px;

height: 500px;

float: left;

}

a{

text-decoration: none;

position: absolute;

top:200px;

display: inline-block;

width: 85px;

line-height: 70px;

background: rgba(3,3,3,.3);

color: #fff;

font-weight: 700;

font-size: 50px;

text-align: center;

display: none;

}

.buttons{

position: absolute;

bottom: 20px;

width: 100%;

text-align: center;

}

span{

width: 15px;

height: 15px;

border-radius: 50%;

display: inline-block;

cursor: pointer;

border: 1px solid #fff;

}

span~span{

margin-left: 20px;

}

.light{

background-color: #fff;

}

js

window.onload = function () {

var index = 1;

var switching = false;

var prev = document.getElementById('prev');

var next = document.getElementById('next');

var list = document.getElementById('list');

var wrap = document.getElementById('wrap');

var dots = document.getElementsByTagName('span');

var buttons = document.getElementById('buttons');

wrap.onmouseover = function () {

prev.style.display = 'block';

next.style.display = 'block';

stop();

};

wrap.onmouseout = function () {

prev.style.display = 'none';

next.style.display = 'none';

play();

}

function lastImg() {

if (switching) {

return;

}

switchPic(900);

index--;

if (index < 1) {

index = 4;

}

else if(index > 4) {

index = 1;

}

lightDot();

}

function nextImg() {

if (switching) {

return;

}

switchPic(-900);

index++;

if (index < 1) {

index = 4;

}

else if(index > 4) {

index = 1;

}

lightDot();

}

function btn(e) {

if (switching) {

return;

}

e = window.e || e;

var target = e.target ? e.target: e.srcElement;

if (target.nodeName.toLowerCase() == 'span') {

var index1 = target.getAttribute('index');

var offset = (index - index1) * 900;

switchPic(offset);

index = index1;

lightDot();

}

};

// 切换图片的函数

function switchPic(offset) {

switching = true;

var time = 300;

var inter = 10; // 隔10ms切换一次

var speed = Math.ceil(offset/(time/inter));

var left = parseInt(list.style.left) + offset;

var go = function () {

var curLeft = parseInt(list.style.left);

if ((speed > 0 && curLeft < left) || (speed < 0 && curLeft > left)) {

list.style.left = curLeft + speed + 'px';

setTimeout(go, inter);

}

else {

list.style.left = left + 'px';

if (left < -3600) {

list.style.left = -900 + 'px';

}

else if (left > -900) {

list.style.left = -3600 + 'px';

}

switching = false;

}

};

go();

}

// 点亮小点

function lightDot() {

for (var i = 0, len = dots.length; i < len; i++) {

if (dots[i].className == 'light') {

dots[i].className = '';

break;

}

}

dots[index-1].className = 'light';

}

// 自动轮播

var timer;

var order;

var interval;

var play = function () {

var interval1 = interval || 2000;

if (order == 'prev') {

timer = setInterval(lastImg, interval1);

}

else {

timer = setInterval(nextImg, interval1);

}

};

var stop = function () {

clearInterval(timer);

};

// 事件绑定DOM2

function addEvent(element, event, listener) {

if (element.addEventListener) {

element.addEventListener(event, listener, false);

}

else {

element.attachEvent('on'+event, listener);

}

}

// 点击左右键切图

addEvent(prev, 'click', lastImg);

addEvent(next, 'click', nextImg);

// 点击小点切图

addEvent(buttons, 'click', btn);

// 指定切换顺序和间隔时间

order = 'next';

interval = 2000;

play();

};

可以建个img文件夹，放几张图片试一下效果，这个是4张图片