

前面介绍了JS左右无缝滚动效果,现在做下无缝滚动——上下的效果。其他代码和左右的差不多,只是改变的是 offsetTop 的值,并且不需要计算 ul 整体的宽度了。
<!DOCTYPE HTML>
<html>
<head>
<meta charset="UTF-8">
<title>无缝滚动——上下</title>
<style type="text/css">
*{margin:0;padding:0;}
li{list-style:none;}
img{border:0;}
#scroll{width:178px;margin:50px auto;position:relative;}
.btn{display:block;width:27px;height:27px;margin-left:auto;margin-right:auto;cursor:pointer;}
.up{background:url(images/up.gif);}
.down{background:url(images/down.gif);}
.content{margin:10px 0;height:440px;overflow:hidden;position:relative;}
.content ul{position:absolute;top:0;left:0;}
.content li{height:110px;}
</style>
</head>
<body>
<div id="scroll">
<a href="javascript:;" id="up" class="btn up"></a>
<div>
<ul>
<li><a href="#" title="111"><img src="images/1.jpg" alt="111" width="178" height="108"/></a></li>
<li><a href="#" title="222"><img src="images/2.jpg" alt="222" width="178" height="108"/></a></li>
<li><a href="#" title="333"><img src="images/3.jpg" alt="333" width="178" height="108"/></a></li>
<li><a href="#" title="444"><img src="images/4.jpg" alt="444" width="178" height="108"/></a></li>
</ul>
</div>
<a class="btn down" href="javascript:;" id="down"></a>
</div>
</body>
</html>
<script type="text/javascript">
window.onload = function(){
var oDiv = document.getElementById('scroll');
var btnUp = document.getElementById('up');
var btnDown = document.getElementById('down');
var oUl = oDiv.getElementsByTagName('ul')[0];
var timer = null;
var speed = -1;
oUl.innerHTML += oUl.innerHTML;
setTimeout(move,1500);
btnUp.onclick = function(){
clearInterval(timer);
speed = -1;
move();
};
btnDown.onclick = function(){
clearInterval(timer);
speed = 1;
move();
};
oUl.onmouseover = function(){
clearInterval(timer);
};
oUl.onmouseout = function(){
move();
};
function move(){
timer = setInterval(function(){
oUl.style.top = oUl.offsetTop + speed + 'px';
if(oUl.offsetTop <= - oUl.offsetHeight / 2){
oUl.style.top = '0';
}else if(oUl.offsetTop >= 0){
oUl.style.top = - oUl.offsetHeight / 2 + 'px';
};
},30);
};
};
</script>如果要改变移动速度,修改 speed 的值即可,初始默认为向上移动,即速度为负数。
希望本文所述对大家JavaScript程序设计有所帮助。
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