请哥哥姐姐们帮我看看这个轮播图为啥实现不了?郁闷
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>轮播图</title>
<style>
ul{
list-style-type: none;
}
.pre{
position: absolute;
left:212px;
top:200px;
width: 22px;
height: 22px;
background:url(images/raw_left.png);
background-size: cover;
}
.next{
position: absolute;
left:1205px;
top:200px;
width: 22px;
height: 22px;
background:url(images/raw_right.png);
background-size: cover;
}
.picc1{
position: absolute;
left: 535px;
top:100px;
opacity: 1;
z-index: 5;
}
.picc2{
position: absolute;
left:450px;
top:111px;
opacity: 0.7;
z-index: 3;
}
.picc3{
position: absolute;
left:365px;
top:122px;
opacity: 0.4;
z-index: 1;
}
.picc4{
position: absolute;
left:784px;
top:122px;
opacity: 0.4;
z-index: 1;
}
.picc5{
position: absolute;
left:660px;
top:111px;
opacity: 0.7;
z-index: 3;
}
</style>
<script>
window.onload=function(){
var opre=document.getElementsByClassName('pre');
var onext=document.getElementsByClassName('next');
ali=document.getElementsByTagName("li");
var arr=[];
for(var i=0;i<ali.length;i++){
var oimg=ali[i].getElementsByTagName('img')[0];
arr.push([parseInt(getStyle(ali[i],'left')),parseInt(getStyle(ali[i],'top')),getStyle(ali[i],'opacity')*100,getStyle(ali[i],'zindex'),oimg.width]);
}
opre.onclick=function(){
arr.push(arr[0]);
arr.shift();
for(var i=0;i<ali.length;i++){
var oimg=ali[i].getElementsByTagName('img')[0];
ali[i].style.zIndex=arr[i][3];
startMove(ali[i],{left:arr[i][0],top:arr[i][1],opacity:arr[i][2]});
startMove(oimg,{width:arr[i][4]});
}
}
onext.onclick=function(){
arr.unshift(arr[arr.length-1]);
arr.pop();
for(var i=0;i<ali.length;i++){
var oimg=ali[i].getElementsByTagName('img')[0];
ali[i].style.zIndex=arr[i][3];
startMove(ali[i],{left:arr[i][0],top:arr[i][1],opacity:arr[i][2]});
startMove(oimg,{width:arr[i][4]});
}
}
}
function startMove(obj,json,endFn){
clearInterval(obj.timer);
obj.timer = setInterval(function(){
var bBtn = true;
for(var attr in json){
var iCur = 0;
if(attr == 'opacity'){
if(Math.round(parseFloat(getStyle(obj,attr))*100)==0){
iCur = Math.round(parseFloat(getStyle(obj,attr))*100);
}
else{
iCur = Math.round(parseFloat(getStyle(obj,attr))*100) || 100;
}
}
else{
iCur = parseInt(getStyle(obj,attr)) || 0;
}
var iSpeed = (json[attr] - iCur)/20;
iSpeed = iSpeed >0 ? Math.ceil(iSpeed) : Math.floor(iSpeed);
if(iCur!=json[attr]){
bBtn = false;
}
if(attr == 'opacity'){
obj.style.filter = 'alpha(opacity=' +(iCur + iSpeed)+ ')';
obj.style.opacity = (iCur + iSpeed)/100;
}
else{
obj.style[attr] = iCur + iSpeed + 'px';
}
}
if(bBtn){
clearInterval(obj.timer);
if(endFn){
endFn.call(obj);
}
}
},30);
}
function getStyle(obj,attr){
if(obj.currentStyle){
return obj.currentStyle[attr];
}
else{
return getComputedStyle(obj,false)[attr];
}
}
</script>
</head>
<body>
<div class="pre"></div>
<div class="next"></div>
<ul>
<li class="picc1"><img src="images/raw_1526215180.jpeg" width="368px" alt=""></li>
<li class="picc2"><img src="images/raw_1526215180.jpeg" width="326px" alt=""></li>
<li class="picc3"><img src="images/raw_1526215180.jpeg" width="284px" alt=""></li>
<li class="picc4"><img src="images/raw_1526215180.jpeg" width="284px" alt=""></li>
<li class="picc5"><img src="images/raw_1526215180.jpeg" width="326px" alt=""></li>
</ul>
</body>
</html>