无缝滚动改进版支持上下左右滚动（封装成函数）

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<!DOCTYPE HTML>
<html lang="en-US">
<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;position:absolute;left:75px;}
    .up{background:url(images/up.gif);top:0;}
    .down{background:url(images/down.gif);top:490px;}
    .content{height:440px;overflow:hidden;position:relative;top:40px;}
    .content ul{position:absolute;top:0;left:0;}
    .content li{height:110px;}
    </style>
</head>
<body>
    <div id="scroll">
        <a href="javascript:;" class="btn up"></a>
        <a href="javascript:;" class="btn down"></a>
        <div class="content">
            <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>
    </div>
</body>
</html>
<script type="text/javascript" src="scroll.js"></script>
<script type="text/javascript">
window.onload = function(){
    scroll('top',1,1000);
};
</script>            

scroll.js：

复制代码代码如下:

/**********
    功能：实现水平或垂直无缝滚动
    参数：direction方向，总共4个值：left,right,top,bottom
          speed移动距离
          iTime多少时间后开始移动，若不写则页面加载完开始移动
**********/
function scroll(direction,speed,iTime){
    var oDiv = document.getElementById('scroll');
    var oUl = oDiv.getElementsByTagName('ul')[0];
    var aLi = oDiv.getElementsByTagName('li');
    var aBtn = oDiv.getElementsByTagName('a');
    var timer = null;
    var iSpeed = 0;
    var flag = true;    //判断水平移动还是垂直移动

    oUl.innerHTML += oUl.innerHTML;

    switch(direction){
        case 'left':
            iSpeed = -speed;
            oUl.style.width = aLi[0].offsetWidth * aLi.length + 'px';
            flag = true;
            break;
        case 'right':
            iSpeed = speed;
            oUl.style.width = aLi[0].offsetWidth * aLi.length + 'px';
            flag = true;
            break;
        case 'top':
            iSpeed = -speed;
            flag = false;
            break;
        case 'bottom':
            iSpeed = speed;
            flag = false;
            break;
    };

    setTimeout(move,iTime);

    //左按钮和上按钮
    aBtn[0].onclick = function(){
        clearInterval(timer);
        iSpeed = -speed;
        move();
    };

    //右按钮和下按钮
    aBtn[1].onclick = function(){
        clearInterval(timer);
        iSpeed = speed;
        move();
    };

    oUl.onmouseover = function(){
        clearInterval(timer);
    };

    oUl.onmouseout = function(){
        move();
    };

    function move(){    
        timer = setInterval(function(){
            if(flag){
                oUl.style.left = oUl.offsetLeft + iSpeed + 'px';
                if(oUl.offsetLeft < -oUl.offsetWidth / 2){
                    oUl.style.left = '0';
                }else if(oUl.offsetLeft > 0){
                    oUl.style.left = - oUl.offsetWidth / 2 + 'px';
                }
            }else{
                oUl.style.top = oUl.offsetTop + iSpeed + 'px';
                if(oUl.offsetTop <= - oUl.offsetHeight / 2){
                    oUl.style.top = '0';
                }else if(oUl.offsetTop >= 0){
                    oUl.style.top = - oUl.offsetHeight / 2 + 'px';
                };
            };
        },30);
    };
};