offsetleft为什么我写的无缝滚动offsetleft一直是0

js中，style.left和offesetleft区别，为什么这里不能相互使用

ni的css属性left 除非是内联样式，或通过style.left赋值了，才有，不然即使有定位，通过n1.style.left取过来的也是null。 var?left=0; var?elem=n1; do{ ????left+=elem.offsetLeft;//距上个定位点距离 ????if(elem.tagName!="BODY"){//忽略窗口滚动条 ????????left-=elem.scrollLeft; ????}; }while(elem=elem.offsetParent); //left就好了... if(left==195){movecaption();}

为什么我写的无缝滚动offsetleft一直是0

<!DOCTYPE> <html> <head> <meta?"?align="center"> <table?cellpadding="2"?cellspacing="0"?border="0"> <tr?align="center"> <td><p><img?src="/jscss/demoimg/200907/bg3.jpg"></p></td> <td><p><img?src="/jscss/demoimg/200907/bg3.jpg"></p></td> <td><p><img?src="/jscss/demoimg/200907/bg3.jpg"></p></td> <td><p><img?src="/jscss/demoimg/200907/bg3.jpg"></p></td> <td><p><img?src="/jscss/demoimg/200907/bg3.jpg"></p></td> <td><p><img?src="/jscss/demoimg/200907/bg3.jpg"></p></td> <td><p><img?src="/jscss/demoimg/200907/bg3.jpg"></p></td> </tr> </table> </td> <td?id="colee_left2"?valign=&"></td> </tr> </table> </div> <script> //使用div时，请保证colee_left2与colee_left1是在同一行上. var?speed=30//速度数值越大速度越慢 var?colee_left2=document.getElementById("colee_left2"); var?colee_left1=document.getElementById("colee_left1"); var?colee_left=document.getElementById("colee_left"); colee_left2.innerHTML=colee_left1.innerHTML function?Marquee3(){ if(colee_left2.offsetWidth-colee_left.scrollLeft<=0)//offsetWidth?是对象的可见宽度 colee_left.scrollLeft-=colee_left1.offsetWidth//scrollWidth?是对象的实际内容的宽，不包边线宽度 else{ colee_left.scrollLeft++ } } var?MyMar3=setInterval(Marquee3,speed) colee_left.onmouseover=function()?{clearInterval(MyMar3)} colee_left.onmouseout=function()?{MyMar3=setInterval(Marquee3,speed)} </script> <!--向左滚动代码结束--> <br> <!--下面是向右滚动代码--> <div?id="colee_right"?style="overflow:hidden;width:500px;"> <table?cellpadding="0"?cellspacing="0"?border="0"> <tr><td?id="colee_right1"?valign=&"?align="center"> <table?cellpadding="2"?cellspacing="0"?border="0"> <tr?align="center"> <td><p><img?src="/jscss/demoimg/200907/bg3.jpg"></p></td> <td><p><img?src="/jscss/demoimg/200907/bg3.jpg"></p></td> <td><p><img?src="/jscss/demoimg/200907/bg3.jpg"></p></td> <td><p><img?src="/jscss/demoimg/200907/bg3.jpg"></p></td> <td><p><img?src="/jscss/demoimg/200907/bg3.jpg"></p></td> </tr> </table> </td> <td?id="colee_right2"?valign=&"></td> </tr> </table> </div> <script> var?speed=30//速度数值越大速度越慢 var?colee_right2=document.getElementById("colee_right2"); var?colee_right1=document.getElementById("colee_right1"); var?colee_right=document.getElementById("colee_right"); colee_right2.innerHTML=colee_right1.innerHTML function?Marquee4(){ if(colee_right.scrollLeft<=0) colee_right.scrollLeft+=colee_right2.offsetWidth else{ colee_right.scrollLeft-- } } var?MyMar4=setInterval(Marquee4,speed) colee_right.onmouseover=function()?{clearInterval(MyMar4)} colee_right.onmouseout=function()?{MyMar4=setInterval(Marquee4,speed)} </script> <!--向右滚动代码结束--> </body> </html>