Javascript getElementsByTagName().length 返回零
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getElementsByTagName().length returns zero
提问by mobius
I am trying to do a simple thing such as:
我正在尝试做一件简单的事情，例如：
var elements = document.getElementsByTagName("input");
console.log(elements);
console.log(elements.length);
The console.log(elements) shows the NodeList containing 28 input elements, but the elements.length is always 0.
console.log(elements) 显示包含 28 个输入元素的 NodeList，但 elements.length 始终为 0。
I've also seen this getElementsByTagName("div").length returns zero for any webpagehowever I didn't understand what exactly is the reason for it happening and how to fix it. I've also noticed that this happens on both Firefox, IE, Chrome.
我还看到这个getElementsByTagName("div").length 对于任何网页都返回零，但是我不明白它发生的确切原因是什么以及如何修复它。我还注意到这在 Firefox、IE、Chrome 上都会发生。
Anyone could help me out?
任何人都可以帮助我吗？
采纳答案by c-smile
NodeListis a live collection and non-deferred scripts execute immediately (see script defer).
NodeList是一个实时集合，非延迟脚本会立即执行（请参阅脚本延迟）。
Try this and you will get an idea of what happens:
试试这个，你会知道会发生什么：
<html>
<head>
<title></title>
<style></style>
<script type="text/javascript">
var elements = document.getElementsByTagName("div");
alert(elements.length);
</script>
</head>
<body>
<div>1</div>
<script type="text/javascript">
//var elements = document.getElementsByTagName("div");
alert(elements.length);
</script>
</body>
</html>
