手把手原生js简单轮播图

<!DOCTYPE html>
<html>

<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
* {
margin: 0;
padding: 0;
text-decoration: none;
}

body {
padding: 20px;
}

#container {
600px;
height: 400px;
border: 3px solid #333;
overflow: hidden;
position: relative;
}

#list {
4200px;
height: 400px;
position: absolute;
z-index: 1;
}

#list img {
600px;
height: 400px;
float: left;
}

#buttons {
position: absolute;
height: 10px;
100px;
z-index: 2;
bottom: 20px;
left: 250px;
}

#buttons span {
cursor: pointer;
float: left;
border: 1px solid #fff;
10px;
height: 10px;
border-radius: 50%;
background: #333;
margin-right: 5px;
}

#buttons .on {
background: orangered;
}

.arrow {
cursor: pointer;
display: none;
line-height: 39px;
text-align: center;
font-size: 36px;
font-weight: bold;
40px;
height: 40px;
position: absolute;
z-index: 2;
top: 180px;
background-color: RGBA(0, 0, 0, .3);
color: #fff;
}

.arrow:hover {
background-color: RGBA(0, 0, 0, .7);
}

#container:hover .arrow {
display: block;
}

#prev {
left: 20px;
}

#next {
right: 20px;
}
</style>
<script type="text/javascript">
/* 知识点： */
/* this用法 */
/* DOM事件 */
/* 定时器 */

window.onload = function () {
var container = document.getElementById('container');
var list = document.getElementById('list');
var buttons = document.getElementById('buttons').getElementsByTagName('span');
var prev = document.getElementById('prev');
var next = document.getElementById('next');
var index = 1;
var timer;

function play() {
//重复执行的定时器
timer = setInterval(function () {
next.onclick();
}, 2000)
}

function stop() {
clearInterval(timer);
}

prev.onclick = function () {
index -= 1;
if (index < 1) {
index = 5
}
buttonsShow();
animate(600);
};

next.onclick = function () {
//由于上边定时器的作用，index会一直递增下去，我们只有5个小圆点，所以需要做出判断
index += 1;
if (index > 5) {
index = 1
}
animate(-600);
buttonsShow();
};

for (var i = 0; i < buttons.length; i++) {
buttons[i].onclick = function () {
//优化，当前图片点击当前的小圆点不执行以下代码。
if (this.className == "on") {
return;
}
/* 这里获得鼠标移动到小圆点的位置，用this把index绑定到对象buttons[i]上，去谷歌this的用法 */
/* 由于这里的index是自定义属性，需要用到getAttribute()这个DOM2级方法，去获取自定义index的属性*/
var clickIndex = parseInt(this.getAttribute('index'));
var offset = 600 * (clickIndex - index); //这个index是当前图片停留时的index
animate(offset);
index = clickIndex; //存放鼠标点击后的位置，用于小圆点的正常显示
buttonsShow();
}
}

container.onmouseover = stop;
container.onmouseout = play;
play();

}
</script>
</head>

<body>

</body>

</html>

具体看原著 http://www.cnblogs.com/LIUYANZUO/p/5679753.html