代码不起作用，无法读取属性“className”；未定义的

发布于 2024-09-01 21:08:20 字数 871 浏览 9 评论 0原文

这段代码有什么问题？

var divarray = [];
var articleHTML = [];
var absHTML;
var keyHTML;
var bodyHTML = [];
var i = 0;
divarray = document.getElementById("yui-main").getElementsByTagName("div");
for ( var j in divarray) {
    if(divarray[i].className == "articleBody"){
        articleHTML = divarray[i];
        for( var k in articleHTML ){
            bodyHTML[i] = '';
            if(articleHTML[i].className == "issueMiniFeature"){continue;}
            if(articleHTML[i].className == "abstract"){absHTML = articleHTML[i]; continue;}
            if(articleHTML[i].className == "journalKeywords"){keyHTML = articleHTML[i]; continue;}
            bodyHTML[i] = articleHTML[i];
        }
        break;
    }
    i++;
}

我收到的错误是：

TypeError: Cannot read property 'className' of undefined

我正在使用 Google Chrome。

原文

What is wrong with this code?

var divarray = [];
var articleHTML = [];
var absHTML;
var keyHTML;
var bodyHTML = [];
var i = 0;
divarray = document.getElementById("yui-main").getElementsByTagName("div");
for ( var j in divarray) {
    if(divarray[i].className == "articleBody"){
        articleHTML = divarray[i];
        for( var k in articleHTML ){
            bodyHTML[i] = '';
            if(articleHTML[i].className == "issueMiniFeature"){continue;}
            if(articleHTML[i].className == "abstract"){absHTML = articleHTML[i]; continue;}
            if(articleHTML[i].className == "journalKeywords"){keyHTML = articleHTML[i]; continue;}
            bodyHTML[i] = articleHTML[i];
        }
        break;
    }
    i++;
}

The error I get is:

TypeError: Cannot read property 'className' of undefined

I am using Google Chrome.

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守不住的情 2024-09-08 21:08:20

你正在使用一个非常奇怪的循环。

 for (var j in array) {
    // use array[i]
    ++ i
 }

问题是 .getElementsByTagName 不返回数组，而是返回类似数组的接口。例如：

>>> for (var j in document.getElementsByTagName('body')) console.log(j)
0
length
item
namedItem

因此，在 for/in 循环中，i 将上升到 array.length + 2而不是array.length - 1。由于 array[array.length + 2] 不存在，因此当您尝试访问它的属性时，它将返回 undefined 并抛出错误。

总是

for (var i = 0, len = array.length; i < len; ++ i) {
  ...
}

与数组一起使用。

You're using a very strange loop.

 for (var j in array) {
    // use array[i]
    ++ i
 }

The problem is .getElementsByTagName doesn't return an array, but an array-like interface. For example:

>>> for (var j in document.getElementsByTagName('body')) console.log(j)
0
length
item
namedItem

Therefore, in your for/in loop, i will go up to array.length + 2 instead of array.length - 1. Since array[array.length + 2] does not exist, it will return undefined and throw the error when you try to access a property of it.

Just always use

for (var i = 0, len = array.length; i < len; ++ i) {
  ...
}

with arrays.

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燕归巢 2024-09-08 21:08:20

您将 articleHTML 初始化为数组，然后显然将 articleHTML 设置为 HTMLElement (divarray[i])，然后将其视为array (articleHTML[i]) — 这实际上试图获取您从 divarray 中提取的 HTMLElement 的 i 属性，但它不会不存在，然后你尝试获取这个未定义值的className。

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半寸时光 2024-09-08 21:08:20

你的意思：

var divarray = [];
var articleHTML = [];
var absHTML;
var keyHTML;
var bodyHTML = [];
var i = 0;
divarray = document.getElementById("yui-main").getElementsByTagName("div");
for ( var j in divarray) {
    if(divarray[j].className == "articleBody"){
        alert("found");
        articleHTML = divarray[j];
        break;
    }
    bodyHTML[i] = '';
    if(divarray[j].className == "issueMiniFeature"){continue;}
    if(divarray[j].className == "abstract"){absHTML = divarray[j]; continue;}
    if(divarray[j].className == "journalKeywords"){keyHTML = divarray[j]; continue;}
    bodyHTML[i] = divarray[j];
    i++;
}

Did you mean:

var divarray = [];
var articleHTML = [];
var absHTML;
var keyHTML;
var bodyHTML = [];
var i = 0;
divarray = document.getElementById("yui-main").getElementsByTagName("div");
for ( var j in divarray) {
    if(divarray[j].className == "articleBody"){
        alert("found");
        articleHTML = divarray[j];
        break;
    }
    bodyHTML[i] = '';
    if(divarray[j].className == "issueMiniFeature"){continue;}
    if(divarray[j].className == "abstract"){absHTML = divarray[j]; continue;}
    if(divarray[j].className == "journalKeywords"){keyHTML = divarray[j]; continue;}
    bodyHTML[i] = divarray[j];
    i++;
}

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