原生js螺旋运动

window.onload=function(){
var oSpiral=document.getElementById('spiral');
var oUl=oSpiral.getElementsByTagName('ul')[0];
var aLi=oUl.getElementsByTagName('li');
var size=6;
var len=size*size;
var eachSize=50;
var col=0;
var row=0;
var min=0;
var max=size-1;
var arr=[];
var bgArr=[];
oUl.style.width=size*(eachSize+1)+'px';
oUl.style.height=size*(eachSize+1)+'px';
for(var i=0;i<len;i++){
var oLi=document.createElement('li');
oLi.style.width=eachSize+'px';
oLi.style.height=eachSize+'px';
oUl.appendChild(oLi);
}
for(var j=0;j<len;j++){
//aLi[ row * size + col ].innerHTML = j;
arr.push(aLi[row*size+col]);
if(row === min && col < max){
col++;
}else if(col === max && row < max){
row++;
}else if(row ===max && col > min){
col--;
}else if(col === min && row > min){
row--;
}if(row-1===min && col===min){
min++;
max--;
}
}
for(var i=0;i<len;i++){
if(i%4===0){
var n=Math.floor(Math.random()*10);
var bgImg='url(../images/'+n+'.jpg)';
arr[i].style.backgroundImage=bgImg;
bgArr.push([i,bgImg]);
}
}
move();
setInterval(move,1000);
function move(){
for(var i=0;i<aLi.length;i++){
aLi[i].style.backgroundImage='';
aLi[i].className='';
}
for(var i=0;i<bgArr.length;i++){
bgArr[i][0]++;
if(arr[bgArr[i][0]]){
arr[bgArr[i][0]].style.backgroundImage=bgArr[i][1];
arr[bgArr[i][0]].className='active';
arr[bgArr[i][0]].style.animationDelay = -Math.random()*1 + 's';
arr[bgArr[i][0]].style.webkitAnimationDelay = -Math.random()*1 + 's';
}else{
bgArr.pop();
var n=Math.floor(Math.random()*10);
var bgImg='url(../images/'+n+'.jpg)';
bgArr.unshift([0,bgImg]);
}


}
}
}