Javascript 横幅广告在html页面中不可见

我有一个banners.js文件

function addEvent(object, evName, fnName, cap) {
    if (object.attachEvent)
        object.attachEvent("on" + evName, fnName);
    else if (object.addEventListener)
        object.addEventListener(evName, fnName, cap);
}

var nextAd;

function makeBannerAds() {
    var bannerBox = document.createElement("div");
    bannerBox.id = "bannerBox";
    document.body.appendChild(bannerBox);
    for (var i=0; i<adsURL.length; i++) {
        var bannerAd = document.createElement("div");
        bannerAd.className = "bannerAd";
        bannerAd.style.zIndex = i;
        var urlLink = document.createElement("a");
        urlLink.href = adsURL[i];
        var bannerIndex = document.createElement("img");
        bannerIndex.src = "banner" + i +".jpg";
        bannerIndex.style.width="290px";
        bannerIndex.style.height="55px";
        bannerBox.appendChild(bannerAd);
    }
    bannerBox.appendChild(bannerAd);
    setInterval("changeBannerAd()", 10000);
}

function changeBannerAd() {
    var allAds = document.getElementById("bannerBox").childNodes;
    alert('work');
    for(var i=0; i<num; i++) {
        if(allAds.style.zIndex == 0) {
            allAds.style.top = "-50px";
            nextAd = allAds;
        }
    }

    for(var i=0; i<num; i++) {
        allAds.style.zIndex--;

        if(allAds.style.zIndex < 0)
            allAds.style.zIndex = num-1;
    }

    var timeDelay = 0;
    for(var i=-50; i<=0; i++) {
        setTimeout("moveNextAd(" + i + ")", timeDelay);
        timeDelay += 15;
    }
}

function moveNextAd(top) {
    nextAd.style.top = top + ".px" 
}

addEvent(window, "load", makeBannerAds(), false);

javascript没有显示任何错误，并且所有语句都在运行，但图像在页面上不可见。我想不出这个问题。从过去两天开始工作。

新答案： 我想你的一些代码需要修改。我只是根据我认为应该是什么样子来编辑这个

检查新的 我想这可能会让你更亲近

简单地说，问题在于

childNodes（）

返回一个元素数组，因此需要像引用数组一样引用该变量

其次，你没有所有需要的附件

var adsURL = new Array();
adsURL[0] = "testpage0.htm";
...
adsURL[11] = "testpage11.htm";

var nextAd;

var moveNextAd = function (top) {
    nextAd.style.top = top + ".px"
}; //changed this to function as variable, answer explained below

var changeBannerAd = function () {
    var num = adsURL.length
    var allAds = document.getElementById("bannerBox")
    allAds = allAds.childNodes;
    //^^^ here is what was wrong
    // Child nodes returns an array of elements
    // So for allAds, you should reference it with allAds[i]
    for (var i = 0; i < num; i++) {
        if (allAds[i].style.zIndex == 0) {
            allAds[i].style.top = "-50px";
            nextAd = allAds[i++];
        }
    }

    for (var i = 0; i < num; i++) {
        allAds[i].style.zIndex--;

        if (allAds[i].style.zIndex < 0) allAds[i].style.zIndex = num - 1;
    }

    var timeDelay = 0;
    for (var i = -50; i <= 0; i++) {
        setTimeout((function () {
            moveNextAd(" + i + ");
        }()), timeDelay);
        timeDelay += 15;
    }
}; //changed this to function as variable too.

function addEvent(object, evName, fnName, cap) {
    if (object.attachEvent) object.attachEvent("on" + evName, fnName);
    else if (object.addEventListener) object.addEventListener(evName, fnName, cap);
}

function makeBannerAds() {
    var bannerBox = document.createElement("div");
    bannerBox.id = "bannerBox";
    document.body.appendChild(bannerBox);
    for (var i = 0; i < adsURL.length; i++) {
        var bannerAd = document.createElement("div");
        bannerAd.className = "bannerAd";
        bannerAd.style.zIndex = i;
        bannerAd.style.position = "absolute";
        var urlLink = document.createElement("a");
        urlLink.href = adsURL[i];
        var bannerIndex = document.createElement("img");
        bannerIndex.src = "banner" + i + ".jpg";
        bannerIndex.style.width = "290px";
        bannerIndex.style.height = "55px";
        urlLink.appendChild(bannerIndex); //Here is the other problem
        bannerAd.appendChild(urlLink); //All these weren't appended
        bannerBox.appendChild(bannerAd); // to each other
    }
    setInterval((function () {
        changeBannerAd();
    }()), 10000);
}

addEvent(window, "load", makeBannerAds(), false);

var-adsrl=new-Array（）；
adsURL[0]=“testpage0.htm”；
...
adsURL[11]=“testpage11.htm”；
var nextAd；
var moveNextAd=函数（顶部）{
nextAd.style.top=top+“.px”
}; //将其更改为变量函数，答案如下所述
var changebanerad=函数（）{
var num=adsURL.length
var allAds=document.getElementById（“bannerBox”）
allAds=allAds.childNodes；
//^^^这就是问题所在
//子节点返回一个元素数组
//因此，对于allAds，您应该使用allAds[i]引用它
对于（变量i=0；i对于（var i=-50；我感谢您的帮助，现在nextAd.style.top=top+“px”中只有一个问题；它产生了一个错误，无法读取未定义的属性样式。感谢您的帮助。有几个语法错误。但是这段代码对我帮助很大。再次感谢
var adsURL = new Array();
adsURL[0] = "testpage0.htm";
...
adsURL[11] = "testpage11.htm";

var nextAd;

var moveNextAd = function (top) {
    nextAd.style.top = top + ".px"
}; //changed this to function as variable, answer explained below

var changeBannerAd = function () {
    var num = adsURL.length
    var allAds = document.getElementById("bannerBox")
    allAds = allAds.childNodes;
    //^^^ here is what was wrong
    // Child nodes returns an array of elements
    // So for allAds, you should reference it with allAds[i]
    for (var i = 0; i < num; i++) {
        if (allAds[i].style.zIndex == 0) {
            allAds[i].style.top = "-50px";
            nextAd = allAds[i++];
        }
    }

    for (var i = 0; i < num; i++) {
        allAds[i].style.zIndex--;

        if (allAds[i].style.zIndex < 0) allAds[i].style.zIndex = num - 1;
    }

    var timeDelay = 0;
    for (var i = -50; i <= 0; i++) {
        setTimeout((function () {
            moveNextAd(" + i + ");
        }()), timeDelay);
        timeDelay += 15;
    }
}; //changed this to function as variable too.

function addEvent(object, evName, fnName, cap) {
    if (object.attachEvent) object.attachEvent("on" + evName, fnName);
    else if (object.addEventListener) object.addEventListener(evName, fnName, cap);
}

function makeBannerAds() {
    var bannerBox = document.createElement("div");
    bannerBox.id = "bannerBox";
    document.body.appendChild(bannerBox);
    for (var i = 0; i < adsURL.length; i++) {
        var bannerAd = document.createElement("div");
        bannerAd.className = "bannerAd";
        bannerAd.style.zIndex = i;
        bannerAd.style.position = "absolute";
        var urlLink = document.createElement("a");
        urlLink.href = adsURL[i];
        var bannerIndex = document.createElement("img");
        bannerIndex.src = "banner" + i + ".jpg";
        bannerIndex.style.width = "290px";
        bannerIndex.style.height = "55px";
        urlLink.appendChild(bannerIndex); //Here is the other problem
        bannerAd.appendChild(urlLink); //All these weren't appended
        bannerBox.appendChild(bannerAd); // to each other
    }
    setInterval((function () {
        changeBannerAd();
    }()), 10000);
}

addEvent(window, "load", makeBannerAds(), false);