#slider ol li a.active{
background-color: #ffffff;
color: #ff0000;
}

//图片节点
var slider = document.getElementById("slider");
var imgul = slider.getElementsByTagName("ul")[0];
var imglis = imgul.getElementsByTagName("li");
var len = imglis.length;
//图片序列节点
var numol = slider.getElementsByTagName("ol")[0];
var numlinks = numol.getElementsByTagName("a");
//共享序列
var index = 0;
//图片跳转,图片跳转的同时,改变序列节点的跳转
var jump = function () {
return setInterval(function(){
if(index >= len){
index = 0;
}
//图片跳转
imgul.style.left = - (800 * index) + "px";
//改变序列节点样式:首先要清除所有的链接的样式,然后在激活对应的序列节点样式
for (var i = 0; i < len; i++) {
numlinks[i].setAttribute("class","");
}
numlinks[index].setAttribute("class","active");
index++;
},2000);
};
var jumpindex = jump();

//增加序列节点的hover控制: 1. hover后要禁止图片的跳转,显示在当前的图片上,这里就需要清除跳转 2.hover离开后,在当前的图片上做图片的跳转
for (var i = 0; i < len; i++){
//hover
numlinks[i].onmouseover = function () {
clearInterval(jumpindex);
for (var i = 0; i < len; i++) {
numlinks[i].setAttribute("class","");
if (numlinks[i] === this){
index = i;
}
}
imgul.style.left = - (800 * index) + "px";
numlinks[index].setAttribute("class","active");
}
//out
numlinks[i].onmouseout = function(){
jumpindex = jump();
}
}