Javascript找不到id的元素？ [英] Javascript can't find element by id?
问题描述
<html>
<head>
<title>Test javascript</title>
<script type="text/javascript">
var e = document.getElementById("db_info");
e.innerHTML='Found you';
</script>
</head>
<body>
<div id="content">
<div id="tables">
</div>
<div id="db_info">
</div>
</div>
</body>
</html>
如果我使用 alert（e）; 它出现 null ....显然我没有在屏幕上找到任何找到你。我做错了什么？
If I use alert(e); it turns up null.... and obviously I don't get any "found you" on screen. What am I doing wrong?
推荐答案
问题是你试图在元素存在之前访问它。您需要等待页面完全加载。一种可能的方法是使用 onload 处理程序：
The problem is that you are trying to access the element before it exists. You need to wait for the page to be fully loaded. A possible approach is to use the onload handler:
window.onload = function () {
var e = document.getElementById("db_info");
e.innerHTML='Found you';
};
但是，大多数常见的JavaScript库都提供了DOM就绪事件。这是更好的，因为 window.onload 也等待所有图像。在大多数情况下，您不需要这样做。
Most common JavaScript libraries provide a DOM-ready event, though. This is better, since window.onload waits for all images, too. You do not need that in most cases.
另一种方法是在结束< / body> -tag，因为它前面的所有内容都是在执行时加载的。
Another approach is to place the script tag right before your closing </body>-tag, since everything in front of it is loaded at the time of execution, then.
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