javascript 未捕获的类型错误：无法读取未定义的属性“0”

Uncaught TypeError: Cannot read property '0' of undefined

提问by geeta battin

Here I have div with class box-titleand I have spanwith related products and I want to change its text to 'Choose Extra To make It More Special'Why this error is coming please anyone can tell me.

在这里，我有类的 divbox-title和span相关的产品，我想将其文本更改为 'Choose Extra To make It More Special'为什么会出现此错误，请任何人都可以告诉我。

function onloadCall()
{   
    var divs = document.getElementsByClassName('box-title');
    for(var i = 0; i < divs.length; i++)
    {
        var div = divs[i];
        if(!div) break
        var span = div.getElementsByTagName('span')[0];
        if(span[0].innerHTML == 'Related Products') 
            span[0].innerHTML='Choose Extra To make It More Special';
    }
}
window.addEventListener('load', onloadCall, false);

Actually, my HTML tag is like this:

实际上，我的 HTML 标签是这样的：

<div class="box-title"><strong><span>Related Products<span></strong></div>

采纳答案by higuaro

Change:

改变：

if(span[0].innerHTML == 'Related Products') 
    span[0].innerHTML='Choose Extra To make It More Special';

for:

为了：

if(span.innerHTML == 'Related Products') 
    span.innerHTML='Choose Extra To make It More Special';

And it should work.

它应该工作。

Also, you can change the following:

此外，您可以更改以下内容：

var span = div.getElementsByTagName('span')[0];

For:

为了：

var span = div.getElementsByTagName('span');

And leave the other code unchanged. If neither of this works, then make sure that there are any spantags in your html file.

并保持其他代码不变。如果这两种方法都span不起作用，请确保您的 html 文件中有任何标签。

回答by Charles

var span = div.getElementsByTagName('span')[0];
if(span[0].innerHTML == 'Related Products') 
    span[0].innerHTML='Choose Extra To make It More Special';

I see you grabbing the first index of the array and then trying to grab the first index of that when it isn't an array.

我看到您抓取数组的第一个索引，然后在它不是数组时尝试抓取它的第一个索引。

Try:

尝试：

var span = div.getElementsByTagName('span')[0];
if(span.innerHTML == 'Related Products') 
    span.innerHTML='Choose Extra To make It More Special';

回答by Ricardo Alvaro Lohmann

if(!div) {
    break;
}
var span = div.getElementsByTagName('span')[0];
if(span && span.innerHTML == 'Related Products') {
    span.innerHTML = 'Choose Extra To make It More Special';
}

demo

演示