JavaScript 数组问题：无法读取属性“src”未定义的

发布于 2024-12-02 11:09:24 字数 877 浏览 1 评论 0原文

该脚本已在 waterbirds.org 上运行多年。现在由于某种原因它坏了。它抛出“无法读取未定义的属性'src'”错误，我已将其跟踪到 preLoad[j].src （runSlideShow 函数的第一行）作为问题，因为我可以在那里放置图像链接地址并且它可以工作。知道是什么原因造成的吗？

// Waterbird Society Theme for Wordpress
// Rotating image banner applet
//
// Usage:
//<body onLoad='rotate_banner(slideShowSpeed, "Image1.jpg", "Image2.jpg"...)'>



var slideShowSpeed;
var j = 0;
var p;
var preLoad = new Array();

function rotate_banner() {
    var args = rotate_banner.arguments;
    slideShowSpeed = Number(args[0]);
    p = args.length;
    for (i = 0; i < p-1; i++) {
        preLoad[i] = new Image();
        preLoad[i].src = args[i+1];
    }
    runSlideShow();
}

function runSlideShow() {
    document.images['SlideShow'].src = preLoad[j].src;
    j++;

    if (j > (preLoad.length - 1)) j = 0;

    t = setTimeout('runSlideShow()', slideShowSpeed*1000);
}

原文

This script has been running over at waterbirds.org for years. Now it's broken for some reason. It throws a "Cannot read property 'src' of undefined" error and I've tracked it down to preLoad[j].src (first line of runSlideShow function) as the problem because I can put a image link address there and it works. Any idea what's causing the problem?

// Waterbird Society Theme for Wordpress
// Rotating image banner applet
//
// Usage:
//<body onLoad='rotate_banner(slideShowSpeed, "Image1.jpg", "Image2.jpg"...)'>



var slideShowSpeed;
var j = 0;
var p;
var preLoad = new Array();

function rotate_banner() {
    var args = rotate_banner.arguments;
    slideShowSpeed = Number(args[0]);
    p = args.length;
    for (i = 0; i < p-1; i++) {
        preLoad[i] = new Image();
        preLoad[i].src = args[i+1];
    }
    runSlideShow();
}

function runSlideShow() {
    document.images['SlideShow'].src = preLoad[j].src;
    j++;

    if (j > (preLoad.length - 1)) j = 0;

    t = setTimeout('runSlideShow()', slideShowSpeed*1000);
}

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

聆听风音 2024-12-09 11:09:24

您的代码一切正常，除了它是全局运行的，因此所有 var 声明都会创建全局变量。

waterbirds.org 上的确切问题是 j 变量在 preLoad[j] 之前和之前的某处定义 j 等于 < code>96，而 preload[96] 实际上是未定义的。

例如，将您的横幅包装在匿名自执行函数中，以使变量本地化，然后您就完成了：

(function(){

var slideShowSpeed;
var j = 0;
var p;
var preLoad = new Array();

// to keep rotate_banner global, save it as a property of window object
window.rotate_banner = function() {
    var args = rotate_banner.arguments;
    slideShowSpeed = Number(args[0]);
    p = args.length;
    for (i = 0; i < p-1; i++) {
        preLoad[i] = new Image();
        preLoad[i].src = args[i+1];
    }
    runSlideShow();
}

function runSlideShow() {
    document.images['SlideShow'].src = preLoad[j].src;
    j++;

    if (j > (preLoad.length - 1)) j = 0;

    t = setTimeout('runSlideShow()', slideShowSpeed*1000);
}

})()

并记住：全局变量是邪恶的！ =)

Everything is alright with your code except for it is run globally so all var declarations create global variables.

The exact issue on waterbirds.org is that j variable is defined somewhere before and by the moment it comes to preLoad[j] j equals 96, and preload[96] is really undefined.

Wrap your banner in anonymous self-executing function, for example, to make vars local, and you're done:

(function(){

var slideShowSpeed;
var j = 0;
var p;
var preLoad = new Array();

// to keep rotate_banner global, save it as a property of window object
window.rotate_banner = function() {
    var args = rotate_banner.arguments;
    slideShowSpeed = Number(args[0]);
    p = args.length;
    for (i = 0; i < p-1; i++) {
        preLoad[i] = new Image();
        preLoad[i].src = args[i+1];
    }
    runSlideShow();
}

function runSlideShow() {
    document.images['SlideShow'].src = preLoad[j].src;
    j++;

    if (j > (preLoad.length - 1)) j = 0;

    t = setTimeout('runSlideShow()', slideShowSpeed*1000);
}

})()

And remember: global variables are evil! =)

回复收藏 0 原文

~没有更多了~