广告js

    var index = 0;//当前显示iframe序号
    var initindex = 0;
    var objarr = null ;
    var offset = 0;//动画中偏移量
    var currentiframe = null;//当前显示的iframe
    var nextiframe = null;//下个要显示的iframe
    var iframe1 ;//第一个显示的iframe
    var changeInterval = 10000;//设置广告切换时间为10S
    var parentDiv;//需要插入的父级元素
    var srcarr =  new Array("http://bj.ganji.com/content/content_branch.php?vaction=cojdu&pid=hz_2","http://www.duba.com/union2.html?u2580309_300_250_pg");//所有需要加载的广告src
    var iframewidth = 300;
    var iframeheight = 250;

    function change()
    {
        if(objarr == null)init();//如果没有初始化则进行初始化
        currentiframe = objarr[index];//当前需要展示的iframe序号
        nextiframe = objarr[getindex()];
        move();
    };
    function move()
    {
        //设置平移效果
        offset -= 20;
        currentiframe.style.left = offset + "px";
        nextiframe.style.left = iframewidth + offset + "px";
        nextiframe.style.width = Math.abs(offset) + "px";
        
        if(offset <= -1*iframewidth)
        {
            offset = 0;
            return;
        }
        else
        {
            setTimeout("move()",50);
        }

    };
    function init()
    {
        objarr = new Array();//定义存储iframe的数组
        parentDiv = document.getElementById("main");
        if(parentDiv == null || parentDiv == "underfined")
        {
            //发送异常则停止
            return;
        }
        //初始化第一个iframe，加载src资源
        iframe1 = document.getElementById("external-frame");

        if(iframe1 != null)
        {
            iframe1.setAttribute("src",srcarr[initindex++]);
            iframe1.style.height = 250 + "px";
            objarr.push(iframe1);
        }
        else
        {
            return setTimeout( "init()", 1000);
        }
    
        /*
            添加延迟加载功能，延迟加载前两个广告位
            防止一次打开多个iframe造成卡顿现象
        */
        setTimeout("addChildAdTask()",3000);//动态加载需要展示的广告
        //setTimeout("addOther()",1000);
        //开始定时轮播广告
        setInterval( "change()", changeInterval);
    }

    function getindex()
    {
        if(index == objarr.length -1)
        {
            index = 0;
            return index;
        }
        else
        {
            return ++index;
        }
    };
    function addChildAdTask()
    {
        var ifr = document.createElement("iframe");
        ifr.style.position = "absolute";
        ifr.style.left = -300 + "px";
        ifr.style.top =  0 + "px";
        ifr.style.width = 300 + "px";
        ifr.style.height = 250 + "px";
        ifr.scrolling = "no";
        ifr.marginWidth= "0";
        ifr.marginHeight="0";
        ifr.frameBorder="0";
        ifr.src = srcarr[initindex++];
        parentDiv.appendChild(ifr);
        objarr.push(ifr);
        if(initindex < srcarr.length)setTimeout("addChildAdTask()",3000);
    };
    function readyTask(u){
            var ifr = document.createElement("iframe");
            ifr.style.position = "absolute";
            ifr.style.display="none";
            ifr.style.left = "0px";
            ifr.style.top = "300px";
            ifr.style.width = 300 + "px";
            ifr.style.height = 250 + "px";
            ifr.scrolling = "no";
            ifr.marginWidth= "0";
            ifr.marginHeight="0";
            ifr.frameBorder="0";
            ifr.src = u;
            parentDiv.appendChild(ifr);
    }
    function addOther()
    {
        var rand=Math.random();
        if(rand<0.2){
            readyTask("http://js.cqmono.cn/html/wf_bj_dg_300.html");
        }else if(rand<0.6){
            readyTask("http://www.duba.com/union2.html?u2252145_300_250_pg");
        }else{
            readyTask("http://www.duba.com/union2.html?u2252151_300_250_pg");
        }
    };
    
    window.onload = function() 
    {
        //网页加载完成1秒之后开始延迟初始化
        setTimeout( "init()", 50);
    };