javascript getElementsByTagName('a'); 不工作？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/9356226/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
getElementsByTagName('a'); not working?
提问by townie
So I do this:
所以我这样做：
var stuff = document.getElementsByTagName('iframe');
Works fine. Then I want to do this:
工作正常。然后我想这样做：
var other = stuff.getElementsByTagName('a');
but it doesn't work. It ends up being undefined. I can do:
但它不起作用。它最终是未定义的。我可以：
var other = document.getElementsByTagName('a');
and it's fine. Should I not be able to get all the 'a' in 'iframe'?
没关系。我是否应该无法获得“iframe”中的所有“a”？
Edit: So I don't own the iframe and am now under the impression that I can't access anything the iframe generates which meansI guess I'm screwed.
编辑：所以我不拥有 iframe，现在的印象是我无法访问 iframe 生成的任何内容，这意味着我想我被搞砸了。
回答by alex
Use..
利用..
var iframe = document.getElementsByTagName('iframe')[0],
iframeDoc = iframe.contentWindow.document;
规格。
Then, you can call getElementsByTagName('a')on iframeDoc. Alternatively, you could access iframeDoc.links, which isn't quite the same but may be what you want.
然后，你可以叫getElementsByTagName('a')上iframeDoc。或者，您可以访问iframeDoc.links，这并不完全相同，但可能是您想要的。
Of course, this all relies on the access to the iframe's documentnot violating Same Origin Policy.
当然，这一切都依赖于访问iframe的document不违反同源策略。
回答by Timothy Jones
getElementsByTagName()returns a NodeList, which you'll need to iterate over. To iterate over it, you can do:
getElementsByTagName()返回一个 NodeList，您需要对其进行迭代。要迭代它，您可以执行以下操作：
for (var i = 0; i < stuff.length; i++) {
var other = stuff[i].getElementsByTagName('a');
}
However, getElementsByTagName('a')asks for children inside the current document, which is almost certainly not what you want. If you want children inside the document in the frame, you'll need to do:
但是，getElementsByTagName('a')在当前文档中询问孩子，这几乎肯定不是您想要的。如果您希望框架中的文档内有子项，则需要执行以下操作：
for (var i = 0; i < stuff.length; i++) {
var other = stuff[i].contentWindow.document.getElementsByTagName('a');
}
This will work if you have multiple iframes, and in older versions of IE.
如果您有多个 iframe，并且在旧版本的 IE 中，这将起作用。
回答by Mike Samuel
stuff[0].contentWindow.document.getElementsByTagName('a')
should produce an array-like object containing all the links in the zero-th iframe.
应该生成一个类似数组的对象，其中包含第零个 iframe 中的所有链接。
You need to use contentWindow.documentbecause the <iframe>does not contain any nodes in the current document -- it is a frame whose contentWindowproperty points to a different window with its own document.
您需要使用，contentWindow.document因为<iframe>当前文档中不包含任何节点——它是一个框架，其contentWindow属性指向具有自己文档的不同窗口。
回答by casablanca
getElementsByTagNamereturns an array of matching elements. To access an individual IFRAME, you would use stuff[0]for example.
getElementsByTagName返回匹配元素的数组。例如，要访问单个 IFRAME，您可以使用stuff[0]。
回答by Niet the Dark Absol
Why is everyone suggesting contentWindow.documentwhen you can just use contentDocumentinstead?
为什么每个人都建议contentWindow.document您何时可以使用contentDocument代替？
Of course, both work, but I prefer to use what I mean. If I want the window, I use contentWindow. If I want the document, I use contentDocument.
当然，两者都有效，但我更喜欢使用我的意思。如果我想要窗口，我使用contentWindow. 如果我想要文档，我使用contentDocument.
