最近要实现一个滚动新闻效果，在网上查了一些资料，发现基本的实现方法有两种：

1.使用Marquee标签。这个标签的使用我已经转载了一篇比较详细的文章，这个标签的优点是便于使用，缺点是人们已经逐渐不适用它了，许多浏览器不支持，甚至在IE8想，XHTML4.0的loose.dtd是可以的，而去掉loose.dtd却不行。

2.使用div+javascript的方法。这种方法的好处是可以兼容几乎所有的浏览器，并且在可以预料的时间内仍能稳定运行。并且使用div使得网页可以利用现有的css资源实现很多炫目的效果。缺点是需要一定的编程经验和耐心。

使用javascript+div方式的基本原理是一样的，利用scrollTop属性和offsetheight属性来实现移动效果。一般使用两个div，里面的内容是一样的，然后利用两个div拼接，形成不断循环的效果。下面是我找到的两份示例代码，第一份正是我用的代码，可以运行。第二份我没做测试。写出来是为了做个对比，第二份应该是能用的，因为那是我从网站上摘下来的。

第一份代码
复制代码 代码如下:
<div id="layer1" style="overflow-y:hidden;width:120;">
            <div id="layer2">
                <%
                ArrayList announceList = DBTools.getView("select * from sys_announce order by pubdate DESC");
                for (int i = 1; i < announceList.size() && i < 5; i++) {
                    String announceArr[] = (String[]) announceList.get(i);
                    String content = announceArr[1];
                    String date = announceArr[2].substring(announceArr[2].indexOf("-")+1, announceArr[2].indexOf(" "));
                %>
                    <table cellspacing="0" cellpadding="0" border="0" width="43">
                        <tr>
                            <td height="10"/>
                        </tr>
                    </table>
                    <table cellspacing="0" cellpadding="0" border="0" width="136">
                        <tr>
                            <td height="20" width="16" valign="top">
                                <img height="12" width="12" vspace="5" valign="top" src="/UploadFiles/2021-04-02/index_18.gif">                            </td>
                            <td width="108" style="line-height: 20px;" mce_style="line-height: 20px;">
                                <%=content%>&nbsp; <%=date%>
                            </td>
                            <td></td>
                        </tr>
                    </table>
                <%
                }
                %>
            </div>
            <div id="layer3"></div>
        </div>
        <mce:script language="javascript"><!--
            var layerHeight = 100; // 定义滚动区域的高度.100
            var iFrame = 1; // 定义每帧移动的象素.
            var iFrequency = 50; // 定义帧频率.
            var timer; // 定义时间句柄.
            if(document.getElementById("layer2").offsetHeight >= layerHeight)
                document.getElementById("layer1").style.height = layerHeight;
            else
                document.getElementById("layer1").style.height = document.getElementById("layer2").offsetHeight;
            document.getElementById("layer3").innerHTML = document.getElementById("layer2").innerHTML;
            // alert(document.getElementById("layer2").innerHTML);
            function move(){
                if(document.getElementById("layer1").scrollTop >= document.getElementById("layer2").offsetHeight){
                    document.getElementById("layer1").scrollTop -= (document.getElementById("layer2").offsetHeight - iFrame);
                }
                else {
                    document.getElementById("layer1").scrollTop += iFrame;
                }
            }
            timer = setInterval("move()",iFrequency);
            document.getElementById("layer1").onmouseover=function() {clearInterval(timer);}
            document.getElementById("layer1").onmouseout=function() {timer=setInterval("move()",iFrequency);}

// --></mce:script>

第二份代码
复制代码 代码如下:
 <SCRIPT language="JavaScript">
            var strArray=new Array();
            strArray[1]=''
                +'<table width=136 border=0 cellspacing=0 cellpadding=0><tr><td width=16 height=20 valign=top><img src="/UploadFiles/2021-04-02/index_18.gif">                +'<table width=136 border=0 cellspacing=0 cellpadding=0><tr><td width=16 height=20 valign=top><img src="/images/index_18.gif">                +'<table width=136 border=0 cellspacing=0 cellpadding=0><tr><td width=16 height=20 valign=top><img src="/UploadFiles/2021-04-02/index_18.gif">

            strArray[0]=''
                +'<table width=136 border=0 cellspacing=0 cellpadding=0><tr><td width=16 height=20 valign=top><img src="/images/index_18.gif">                +'<table width=136 border=0 cellspacing=0 cellpadding=0><tr><td width=16 height=20 valign=top><img src="/UploadFiles/2021-04-02/index_18.gif">                +'<table width=136 border=0 cellspacing=0 cellpadding=0><tr><td width=16 height=20 valign=top><img src="/images/index_18.gif">        /*
            showId=Math.floor(Math.random()*1);
            tempStr=strArray[showId];
            strArray[showId]=strArray[0];
            strArray[0]=tempStr;
            */
        </SCRIPT>
        <SCRIPT>
            var timer;

            document.write('<div id="icefable1" style="width:136;">'
                +'<table width=130; border=0 cellspacing=0 cellpadding=0>'
                +'<tr><td width=130; height=120 style="padding-top:2px" mce_style="padding-top:2px" valign=top>'+strArray[1]+'</td></tr>'
                +'<tr><td width=130; height=120 style="padding-top:2px" mce_style="padding-top:2px" valign=top>'+strArray[0]+'</td></tr>'
                +'</table>'
                +'</div>'
                +'<div id="icefable2" style="position:absolute;visibility:hidden" mce_style="position:absolute;visibility:hidden"></div>');
            /*
            var marqueesHeight=132;
            var stopscroll=false;
            icefable1.scrollTop=0;
            */
            with(icefable1){
                /*
                style.width=0;
                style.height=marqueesHeight;
                style.overflowX="visible";
                style.overflowY="hidden";
                noWrap=true;
                */
                onmouseover=function(){clearInterval(timer);};
                onmouseout=function(){timer = setInterval("move()",100);};
            }
            /*
            var preTop=0;
            var currentTop=0;
            var stoptime=0;
             */
            function init_srolltext(){
                icefable2.innerHTML="";
                icefable2.innerHTML+=icefable1.innerHTML;
                icefable1.innerHTML=icefable2.innerHTML+icefable2.innerHTML;
                timer = setInterval("move()",100);
            }
            function move(){
                 if(document.getElementById("icefable2").scrollTop >= document.getElementById("icefable1").offsetHeight)
                     document.getElementById("icefable2").scrollTop -= (document.getElementById("icefable1").offsetHeight - 1);
                 else
                     ocument.getElementById("icefable2").scrollTop += 1;
            }
            init_srolltext();

            function scrollUp(){
                if(stopscroll==true) return;
                currentTop+=4;
                if(currentTop==132)
                {
                    stoptime+=4;
                    currentTop-=0;
                }
                else {
                    preTop=icefable1.scrollTop;
                    icefable1.scrollTop+=4;
                    if(preTop==icefable1.scrollTop){
                        icefable1.scrollTop=icefable2.offsetHeight-marqueesHeight;
                        icefable1.scrollTop+=4;
                    }
                }
            }
            //setTimeout("init_srolltext()",2000);
            //init_srolltext();
        </SCRIPT>