<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport"
content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
.mi{
width: 512px;
height: 400px;
margin:100px auto;
overflow: hidden;
position: relative;
}
.mi span{
position: absolute;
left:0;
width:100%;
height: 50%;
cursor: pointer;
}
#picUp{
top:0;
}
#picDown{
bottom:0
}
#pic{
position: absolute;
top:0;
left:0;
}
</style>
</head>
<body>
<div class="mi">
<img src = "images/mi.png">
<span id="picUp"></span>
<span id="picDown"></span>
</div>
<script>
function $(id) {
return document.getElementById(id);
}
var timer = null; // 定义定时器
var count = 0; // 定义top值
// 鼠标悬浮上半部分时，图片向上滚动
$("picUp").onmouseover = function () {
clearInterval(timer); // 清除定时器
timer = setInterval(function () { // 开启定时器
count -= 3;
if(count >= -1070){
$("pic").style.top = count + "px";
}else{
clearInterval(timer);
}
},30)
}
// 鼠标悬浮下半部分时，图片向下滚动
$("picDown").onmouseover = function () {
clearInterval(timer);
timer = setInterval(function () {
count ++;
if(count <= 0){
$("pic").style.top = count + "px";
}else{
clearInterval(timer);
}
},20)
}
// 当鼠标移出时，停止定时器
$("picUp").parentNode.onmouseout = function () {
clearInterval(timer);
}
</script>
</body>
</html>
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