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getElementsByTagName().length returns zero

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臣服心动
臣服心动 2021-01-04 20:17

I am trying to do a simple thing such as:

var elements = document.getElementsByTagName(\"input\");
console.log(elements);
console.log(elements.length);
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3条回答
  • 面向向阳花
    2021-01-04 20:31

    NodeList is a live collection and non-deferred scripts execute immediately (see script defer).

    Try this and you will get an idea of what happens:

    <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>
    0 讨论(0)
  • 傲寒
    2021-01-04 20:36

    This happens because of the asynchronous behaviour of JS. You're trying to display the element's value before it is being rendered. In order to avoid it, you could add the "async" attribute to your tag, as in the following example:

    <script type="text/javascript" src="myTag.js" async></script>
    0 讨论(0)
  • 悲&欢浪女
    2021-01-04 20:47

    your script should have the attribute "deter" to detect the tags

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