How to use JavaScript to achieve the effect of continuous scrolling subtitles

How to use JavaScript to achieve the effect of continuous scrolling subtitles_javascript skills

WBOY

Release： 2016-05-16 15:51:12

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We generally use the Marquee tag to control the scrolling of elements. However, the one-way Marquee scrolling is discontinuous. Every time a scene is scrolled, a blank will appear. The scrolling in the introduction below is continuous without interruption.

Here is an introduction to how this is achieved.

In order for scrolling to be "continuous", we need to copy the content of the subtitles multiple times until the height of the content is no less than twice the height of the scroll area. Then we hide the overflowing scroll bar and use code to control the scroll bar to move downward (at this time the content will move upward). When the scroll bar scrolls to the bottom, theoretically it cannot scroll any further, so we immediately adjust the scroll bar and scroll it up to the same position as the current screen. As a result, what we see is continuous scrolling. Haha, it’s that simple. How about doing it? Let's see how this is achieved step by step.

＜div id="marquees"> ＜!-- 这些是字幕的内容，你可以任意定义 --> ＜a href="#">链接一＜/a>
＜br> ＜a href="#">链接二＜/a>
＜br> ＜a href="#">链接三＜/a>
＜br> ＜a href="#">链接四＜/a>
＜br> ＜!-- 字幕内容结束 -->
＜/div>
＜!-- 以下是java-script代码 -->
＜script language="java-script">
＜!--
marqueesHeight=200; //内容区高度
stopscroll=false; //这个变量控制是否停止滚动
with(marquees){
noWrap=true; //这句表内容区不自动换行
style.width=0; //于是我们可以将它的宽度设为0，因为它会被撑大
style.height=marqueesHeight;
style.overflowY="hidden"; //滚动条不可见
onmouseover=new Function("stopscroll=true"); //鼠标经过，停止滚动
onmouseout=new Function("stopscroll=false"); //鼠标离开，开始滚动
}
//这时候，内容区的高度是无法读取了。下面输出一个不可见的层"templayer"，稍后将内容复制到里面：
document.write('＜div id="templayer"
style="position:absolute;z-index:1;visibility:hidden">＜/div>');
function init(){ //初始化滚动内容
//多次复制原内容到"templayer"，直到"templayer"的高度大于内容区高度：
while(templayer.offsetHeight＜marqueesHeight){
templayer.innerHTML+=marquees.innerHTML;
} //把"templayer"的内容的“两倍”复制回原内容区：
marquees.innerHTML=templayer.innerHTML+templayer.innerHTML;
//设置连续超时，调用"scrollUp()"函数驱动滚动条：
setInterval("scrollUp()",10);
}
document.body.onload=init;
preTop=0; //这个变量用于判断滚动条是否已经到了尽头
function scrollUp(){ //滚动条的驱动函数
if(stopscroll==true) return; //如果变量"stopscroll"为真，则停止滚动
preTop=marquees.scrollTop; //记录滚动前的滚动条位置
marquees.scrollTop+=1; //滚动条向下移动一个像素
//如果滚动条不动了，则向上滚动到和当前画面一样的位置
//当然不仅如此，同样还要向下滚动一个像素(+1)：
if(preTop==marquees.scrollTop){
marquees.scrollTop=templayer.offsetHeight-marqueesHeight+1;
}
}
-->
＜/script>

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That’s it. It doesn’t feel difficult to do.