标头中的JavaScript代码 [英] JavaScript code place in the header
问题描述
我不清楚将其添加到标头部分时，为什么它无法正常运行javascript代码.
I am not clear why its not working the javascript code when I add it to the header section as follows.
我们可以按如下方式在体内放置一个javascript代码
We can place a javascript code within the body as follows
<html>
<head>
<title> Simple Test </title>
</head>
<body>
<div id="mydiv"> This is the div content </div>
<script type="text/javascript" >
document.getElementById("mydiv").innerHTML=Date();
</script>
</body>
</html>
但是，当我将相同的JavaScript代码放在标头部分中时，它是行不通的.
But when I place the same JavaScript code in the header section it doesn't work.
<html>
<head>
<title> Simple Test </title>
<script type="text/javascript" >
document.getElementById("mydiv").innerHTML=Date();
</script>
</head>
有人可以解释这个问题吗?我知道我可以在标头中编写JavaScript函数并在事件中调用它.但是我们不能以这种方式使用.如果不能为什么.
Can Someone please explain the issue. I know I can Write a JavaScript function in header and call it in an event. But can't we Use in this way. If Can't why.
推荐答案
因为加载页面时，当浏览器到达该< script> 元素时，#mydiv元素具有尚未创建.
because when the page is loaded, by the time the browser gets to that <script> element, the #mydiv element has not yet been created.
要么使用"onload"事件，要么将脚本放在页面底部.
either use an "onload" event, or put your scripts at the bottom of the page.
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