var div_imgs = document.getElementById("banner").getElementsByTagName("div");
var imgLeft = [0, 66, 132]; //5个图片的初始left值
var imgWidth = 551; //图片的宽度
var atf = [true, true, true]; //5个图片的位置：true为右边，false为左边
var speed1 = 10, speed2 = 2000, mo = 15; //速度
var sTo;
function jsf_move(n){
 clearTimeout(sTo);
 var thisL; //图片left值
 if (atf[n]) { //要移动的图片在右边
  //需移动的图片（包括该图片左边的所有图片）向左边移动)
  for (var i=0; i<=n; i++) { //当前值-(图片宽度-(当前值-初始值))/速度 
   thisL = parseInt(getStyle(div_imgs[i],"left"));
   div_imgs[i].style.left = thisL - Math.ceil((imgWidth-(imgLeft[i]-thisL))/mo) + "px";
   if (i<n) atf[i] = false; //更改图片的位置状态
  }
 } else { //要移动的图片在左边
  //需移动的图片（包括该图片右边的所有图片）向右边移动)
  for (var i=2; i>=n; i--) { //当前值+(当前值-初始值)/速度
   thisL = parseInt(getStyle(div_imgs[i],"left"));
   div_imgs[i].style.left = thisL + Math.ceil(Math.abs(thisL-imgLeft[i])/mo) + "px";
   if (i>n) atf[i] = true; //更改图片的位置状态
  }
 }
 thisL = parseInt(getStyle(div_imgs[n],"left"));
 if ((atf[n]  &&  thisL>(imgLeft[n]-imgWidth)) || (!atf[n]  &&  thisL<imgLeft[n])) {
  //当前图片移动未结束，继续移动当前图片
  sTo = setTimeout(function(){jsf_move(n);}, speed1);
 } else {
  //当前图片移动结束，准备移动下一张图片
  if (n>=1  &&  atf[n]) {
   atf[n] = false;
   sTo = setTimeout(function(){jsf_move(n);}, speed2);
  } else if (n==0  &&  !atf[n]) {
   atf[n] = true;
   sTo = setTimeout(function(){jsf_move(n);}, speed2);
  } else if (atf[n]){
   atf[n] = false;
   sTo = setTimeout(function(){jsf_move(++n);}, speed2);
  } else {
   sTo = setTimeout(function(){jsf_move(--n);}, speed2);
  }
 }
}
 function jsf_mmove(n){
 clearTimeout(sTo);
 switch (n){
 case 0 :
  atf[0] = false;
  jsf_move(0);
  break;
 case 1 :
 case 2 :
  if (atf[n-1]) {
   sTo = setTimeout(function(){jsf_move(n-1);}, speed1);
  } else if (atf[n]) {
   atf[n-1] = true;
   sTo = setTimeout(function(){jsf_move(n-1);}, speed1);
  } else {
   sTo = setTimeout(function(){jsf_move(n);}, speed1);

  }
  break;
 case 3 :
  atf = [false, false, true, true];
  jsf_move(2);
  break; 
 }
}
window.onload = function(){
 sTo = setTimeout("jsf_move(0)",speed2);
}
function getStyle( elem, name ) {
 if (elem.style[name]) { return elem.style[name]; }
 else if (elem.currentStyle) { return elem.currentStyle[name]; }
 else if (document.defaultView  &&  document.defaultView.getComputedStyle) {
  name = name.replace(/([A-Z])/g,"-$1");
  name = name.toLowerCase();
  var s = document.defaultView.getComputedStyle(elem,"");
  return s  &&  s.getPropertyValue(name);
 }
 else { return null; }
}