总结：
function 函数名称（参数）{
var声明一个变量=document.getElementById（）在文档中找括号中的id
var声明一个变量=a.document.getElementByTabName（）在变量a中找a标签
for（i=0；i<a_a.length;//i小于变量a_a的长度；i++）{
a_a[i].style.display="none"//把变量a_a里面的a隐藏
}
a_a[参数].style.display=“block”"//把变量a_a里面的a显示
}
实例
<!DOCTYPE html>
<html>
<head>
<title>123</title>
<meta charset="utf-8">
<link rel="icon" type="image/x-icon" href="static/images/favicon.ico">
<style type="text/css">
div{height: 300px;width: 500px;position: relative;margin:50px auto;overflow: hidden;}
img{height: 300px;width: 500px; }
p{display:inline-block;width: 500px;height: 30px;position: absolute;bottom:0;color: #fff;text-align: center;margin: 20px auto;}
p span{display:inline-block;width: 20px;height: 20px;border:20px;background: rgba(254,254,254,0.6);border-radius: 50%;line-height: 20px;text-align:center;cursor:pointer;}
</style>
</head>
<body>
<div id="banner">
<a href=""><img src="static/images/1.jpg"></a>
<a href=""><img src="static/images/2.jpg"></a>
<a href=""><img src="static/images/3.jpg"></a>
<a href=""><img src="static/images/4.jpg"></a>
<a href=""><img src="static/images/5.jpg"></a>
<p>
<span onclick="ban(0)">1</span>
<span onclick="ban(1)">2</span>
<span onclick="ban(2)">3</span>
<span onclick="ban(3)">4</span>
<span onclick="ban(4)">5</span>
</p>
<script type="text/javascript">
function ban(ner){
var a=document.getElementById('banner');
var a_a=a.getElementsByTagName('a');
for(var i=0;i<a_a.length;i++){
a_a[i].style.display="none";
}
a_a[ner].style.display="block"
}
</script>
</div>
</body>
</html>运行实例 »
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