即使元素存在，getElementById() 也会返回 null
我尝试使用 getElementById() 获取元素，但即使该元素存在，它也会返回 null。我做错了什么？
<html>
<head>
<title>blah</title>
<script type="text/javascript">
alert(document.getElementById("abc"));
</script>
</head>
<body>
<div id="abc">
</div>
</body>
I'm trying to get the element with getElementById(), but it returns null even though the element exists. What am I doing wrong?
<html>
<head>
<title>blah</title>
<script type="text/javascript">
alert(document.getElementById("abc"));
</script>
</head>
<body>
<div id="abc">
</div>
</body>
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评论（5）
您必须将其放入
documentload事件中。执行脚本时，DOM 尚未到达abc。You have to put this in a
documentloadevent. The DOM hasn't gotten toabcby the time the script is executed.您的脚本在 DOM 加载之前运行。要解决此问题，您可以将代码放置在
window.onload函数中，如下所示：另一种方法是将您的
script放置在结束之前。标签。Your script runs before the DOM has been loaded. To fix this you can place your code in the
window.onloadfunction like so:An alternative is to place your
scriptright before the closing</body>tag.如果您不想附加到加载事件，则只需将脚本放在正文的底部，这样它将在最后执行 -
If you don't want to attach to the load event then simply put your script at the bottom of the body, so it will execute at the end-
这是因为脚本在页面呈现之前运行。
为了证明这一点，请将此属性添加到 body 标记中：
This is because the script runs before the page has rendered.
For proof add this attribute to the body tag:
但它并不存在，在 HTML 中不存在。 HTML 文档是从上到下解析的，就像程序运行一样。最好的解决方案是将脚本标签放在页面底部。您还可以将 JavaScript 附加到 onload 事件。
But it doesn't exist, not at that point in the HTML. HTML documents are parsed top-to-bottom, just like programs run. The best solution is just to put your script tag at the bottom of the page. You could also attach your JavaScript to the onload event.