JavaScript无缝滚动动画优化：更简洁的代码与新一代实现方案

新一代无缝滚动函数的设计思路

追求以精简代码达成相同效果是编程的终极目标，同时需确保代码可读性。在《基于javascript的无缝滚动动画实现1》的最后一个运行示例中，我已进行了相关探索。尽管形式有所变化，核心逻辑仍围绕scrollTop/scrollLeft与offsetTop/offsetLeft展开。基本思路是让包含图片或文字的元素整体向指定方向移动，当移动距离达到特定阈值后重置至原点。为防止内容移出视野，需准备两套相同的内容。在第一部分中，第二套内容是动态生成并复制到兄弟元素中的，这在水平滚动时需要额外处理以排列所有内容。我在思考，若将第二套内容直接追加到原元素中，是否能提升效果并减少CSS编写？此外，使用scrollTop/scrollLeft实现滚动对父容器的宽高有严格限制。例如，若ul为容器、li中的图片为滚动内容，且每张图片尺寸相等，则ul的高度至少需为图片高度的两倍，否则无法滚动。鉴于此，我开发了新一代的无缝滚动函数。


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</ul>


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<!doctype html>
<title>javascript无缝滚动 by 司徒正美</title>
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<h1>javascript无缝滚动(向上滚动) by 司徒正美</h1>
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</ul>

垂直与水平滚动的具体实现

实现向下滚动相对容易，只需初始时将内容定位在第一套与第二套内容之间，即slide.offsetHeight的位置。但需注意将该值取负，以便实现整体向下移动，随后再逐渐向上移动。


 
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<style type="text/css">
 h1 {
 font:400 16px/1 "Microsoft YaHei",KaiTi_GB2312,SimSun
 }
 #marquee ,#marquee li {
 padding:0;
 margin:0;
 }
 #marquee {
 position:relative;
 list-style:none;
 height:150px;
 width:200px;
 overflow:hidden;
 border:10px solid #B45B3E;
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 position:absolute;
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 display:block;
 border:0;
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</style>
<script type="text/javascript">
 var Marquee = function(id){
 try{document.execCommand("BackgroundImageCache", false, true);}catch(e){};
 var container = document.getElementById(id),
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 speed = arguments[1] || 10,
 critical = slide.offsetHeight,//临界值
 delta = -critical;
 slide.innerHTML += slide.innerHTML;
 var rolling = function(){
  delta == 0 ? delta = -critical : delta++;
  slide.style.top = delta + "px";
 }
 var timer = setInterval(rolling,speed)//设置定时器
 container.onmouseover=function() {clearInterval(timer)}//鼠标移到marquee上时，清除定时器，停止滚动
 container.onmouseout=function() {timer=setInterval(rolling,speed)}//鼠标移开时重设定时器
 }
 window.onload = function(){
 Marquee("marquee");
 }
</script>
<h1>javascript无缝滚动(向下滚动) by 司徒正美</h1>
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 </li>
</ul>

水平移动的实现比第一部分更为简便，结构层无需任何改动，表现层的修改也极少。


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 padding:0;
 margin:0;
}
#marquee {
 position:relative;
 list-style:none;
 height:150px;
 width:200px;
 overflow:hidden;
 border:10px solid #B45B3E;
}
#marquee li {
 position:absolute;
 width:1000%;/*★★新增加★★*/
}
#marquee a {
 float:left;/*★★新增加★★*/
}
#marquee img {
 display:block;
 border:0;
}

难点在于确定临界值，即第一套内容与第二套内容之间的分界位置。由于第二套内容未包裹额外元素，需从滚动对象入手。因滚动对象均为a元素，需计算第二套内容的第一个a元素距离父元素左侧的距离，该值即为所求临界值。理解这一点后，实现便变得轻松。


 //*************略********* 
 slide.innerHTML += slide.innerHTML;
 var item = slide.getElementsByTagName("a"),
 critical = item[item.length/2].offsetLeft,//临界值
//*************略*********


 
<!doctype html>
<title>javascript无缝滚动 by 司徒正美</title>
<meta charset="utf-8"/>
<meta name="keywords" content="javascript无缝滚动 by 司徒正美" />
<meta name="description" content="javascript无缝滚动 by 司徒正美" />
<base href="http://images.cnblogs.com/cnblogs_com/rubylouvre/199042/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >
<style type="text/css">
 h1 {
 font:400 16px/1 "Microsoft YaHei",KaiTi_GB2312,SimSun
 }
 #marquee ,#marquee li {
 padding:0;
 margin:0;
 }
 #marquee {
 position:relative;
 list-style:none;
 height:150px;
 width:200px;
 overflow:hidden;
 border:10px solid #8080C0;
 }
 #marquee li {
 position:absolute;
 width:1000%;/*新增加*/
 }
 #marquee a {
 float:left;/*新增加*/
 }
 #marquee img {
 display:block;
 border:0;
 }
</style>
<script type="text/javascript">
 var Marquee = function(id){
 try{document.execCommand("BackgroundImageCache", false, true);}catch(e){};
 var container = document.getElementById(id),
 slide = container.getElementsByTagName("li")[0],
 speed = arguments[1] || 10;
 slide.innerHTML += slide.innerHTML;
 var item = slide.getElementsByTagName("a"),
 critical = item[item.length/2].offsetLeft,//临界值
 delta = 0;
 var rolling = function(){
  delta == -critical ? delta = 0 : delta--;
  slide.style.left = delta + "px";
 }
 var timer = setInterval(rolling,speed)//设置定时器
 container.onmouseover=function() {clearInterval(timer)}//鼠标移到marquee上时，清除定时器，停止滚动
 container.onmouseout=function() {timer=setInterval(rolling,speed)}//鼠标移开时重设定时器
 }
 window.onload = function(){
 Marquee("marquee");
 }
</script>
<h1>javascript无缝滚动(向左滚动) by 司徒正美</h1>
<base href="http://images.cnblogs.com/cnblogs_com/rubylouvre/199042/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >
<ul id="marquee">
 <li>
 <a href="http://www.cnblogs.com/rubylouvre/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="o_s017.jpg" alt="无缝滚动"/></a>
 <a href="http://www.cnblogs.com/rubylouvre/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="o_s018.jpg" alt="无缝滚动"/></a>
 <a href="http://www.cnblogs.com/rubylouvre/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="o_s019.jpg" alt="无缝滚动"/></a>
 <a href="http://www.cnblogs.com/rubylouvre/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="o_s020.jpg" alt="无缝滚动"/></a>
 <a href="http://www.cnblogs.com/rubylouvre/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="o_s021.jpg" alt="无缝滚动"/></a>
 <a href="http://www.cnblogs.com/rubylouvre/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="o_s022.jpg" alt="无缝滚动"/></a>
 <a href="http://www.cnblogs.com/rubylouvre/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="o_s023.jpg" alt="无缝滚动"/></a>
 </li>
</ul>

向右滚动与函数合并优化

以下是向右滚动的代码。由于脚本不足20行，查看源码即可理解，此处不再赘述。


 
<!doctype html>
<title>javascript无缝滚动 by 司徒正美</title>
<meta charset="utf-8"/>
<meta name="keywords" content="javascript无缝滚动 by 司徒正美" />
<meta name="description" content="javascript无缝滚动 by 司徒正美" />
<base href="http://images.cnblogs.com/cnblogs_com/rubylouvre/199042/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >
<style type="text/css">
 h1 {
 font:400 16px/1 "Microsoft YaHei",KaiTi_GB2312,SimSun
 }
 #marquee ,#marquee li {
 padding:0;
 margin:0;
 }
 #marquee {
 position:relative;
 list-style:none;
 height:150px;
 width:200px;
 overflow:hidden;
 border:10px solid #6cc;
 }
 #marquee li {
 position:absolute;
 width:1000%;
 }
 #marquee a {
 float:left;
 }
 #marquee img {
 display:block;
 border:0;
 }
</style>
<script type="text/javascript">
 var Marquee = function(id){
 try{document.execCommand("BackgroundImageCache", false, true);}catch(e){};
 var container = document.getElementById(id),
 slide = container.getElementsByTagName("li")[0],
 speed = arguments[1] || 10;
 slide.innerHTML += slide.innerHTML;
 var item = slide.getElementsByTagName("a"),//临界点
 critical = item[item.length/2].offsetLeft,
 delta = -critical;
 var rolling = function(){
  delta == 0 ? delta = -critical : delta++;
  slide.style.left = delta + "px";
 }
 var timer = setInterval(rolling,speed)//设置定时器
 container.onmouseover=function() {clearInterval(timer)}//鼠标移到marquee上时，清除定时器，停止滚动
 container.onmouseout=function() {timer=setInterval(rolling,speed)}//鼠标移开时重设定时器
 }
 window.onload = function(){
 Marquee("marquee");
 }
</script>
<h1>javascript无缝滚动(向右滚动) by 司徒正美</h1>
<base href="http://images.cnblogs.com/cnblogs_com/rubylouvre/199042/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >
<ul id="marquee">
 <li>
 <a href="http://www.cnblogs.com/rubylouvre/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="o_s017.jpg" alt="无缝滚动"/></a>
 <a href="http://www.cnblogs.com/rubylouvre/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="o_s018.jpg" alt="无缝滚动"/></a>
 <a href="http://www.cnblogs.com/rubylouvre/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="o_s019.jpg" alt="无缝滚动"/></a>
 <a href="http://www.cnblogs.com/rubylouvre/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="o_s020.jpg" alt="无缝滚动"/></a>
 <a href="http://www.cnblogs.com/rubylouvre/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="o_s021.jpg" alt="无缝滚动"/></a>
 <a href="http://www.cnblogs.com/rubylouvre/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="o_s022.jpg" alt="无缝滚动"/></a>
 <a href="http://www.cnblogs.com/rubylouvre/" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ><img src="o_s023.jpg" alt="无缝滚动"/></a>
 </li>
</ul>

可将上述四个函数合并为一个统一函数，结构层与表现层可参照向上滚动的示例。


var Marquee = function(id){
 try{document.execCommand("BackgroundImageCache", false, true);}catch(e){};
 var container = document.getElementById(id),
 slide = container.getElementsByTagName("li")[0],
 options = arguments[1] || {},
 speed = options.speed || 10,
 direction = options.direction || "left";
 slide.innerHTML += slide.innerHTML;
 var item = slide.getElementsByTagName("a"),
 critical,delta,rolling,field;
 if(direction == "left" || direction == "right"){
 slide.style.cssText = "width:1000%";
 for(var i=0 ,l=item.length; i<l;i++){
  item[i].style.cssText = "float:left";
 }
 field = "left";
 critical = item[item.length/2].offsetLeft;
 }else if(direction == "up" || direction == "down"){
 field = "top";
 critical = item[item.length/2].offsetTop;
 }
 if(direction == "up" || direction == "left"){
 delta = 0;
 rolling = function(){
  delta == -critical ? delta = 0 : delta--;
  slide.style[field] = delta + "px";
 }
 }else if(direction == "down" || direction == "right"){
 delta = -critical;
 rolling = function(){
  delta == 0 ? delta = -critical : delta++;
  slide.style[field] = delta + "px";
 }
 }
 var timer = setInterval(rolling,speed)//设置定时器
 container.onmouseover=function() {clearInterval(timer)}//鼠标移到marquee上时，清除定时器，停止滚动
 container.onmouseout=function() {timer=setInterval(rolling,speed)}//鼠标移开时重设定时器
}

使用方式如下：


Marquee("marquee",{speed:35,direction:"up"});

借助此函数，实现另一种图片轮换将变得容易，此处先作预告。本文到此结束。

至此，关于基于javascript的无缝滚动动画实现2的介绍完毕。如需了解更多javascript无缝滚动相关内容，请搜索本站过往文章或继续浏览后续相关文章。希望大家今后多多支持本站！

基于JavaScript的无缝滚动动画实现2

新一代无缝滚动函数的设计思路

垂直与水平滚动的具体实现

向右滚动与函数合并优化

实用工具推荐