未捕获的ReferenceError：当jquery.js位于文档末尾时，未定义$ [英] Uncaught ReferenceError: $ is not defined when jquery.js is at end of document
问题描述
我有一个项目，其中所有JS文件都在页脚中引用，建议用于页面加载的速度，包括指向Jquery文件的链接。这段代码产生一个未捕获的ReferenceError，我假设因为在调用脚本之前尚未定义Jquery：
I have a project where all the JS files are referenced in the footer, as is recommended for speed of page loading, including the link to the Jquery file. This code produces an "Uncaught ReferenceError", I assume because Jquery has not been defined before my script is called:
<html>
<head>
<link rel="stylesheet" type="text/css" href="css/bootstrap.css">
</head>
<body>
<p>
<a href="#" data-toggle="popover" title="first popover" id="example">hover over me</a>
</p>
<script type="text/javascript">
$(function(){
$('#example').popover({ trigger:'hover' });
})
</script>
<script type="text/javascript" src="js/jquery.min.js"></script>
<script type="text/javascript" src="js/bootstrap.js"></script>
</body>
</html>
如果我将Jquery链接移动到标题，那么代码运行正常，但这会减慢页面加载时间。
If I move the Jquery link to the header, then the code runs fine, but this will slow the page loading time.
有没有更好的方法来声明我的函数，以便它不会抛出此UncaughtReference错误，或者保持头部中的Jquery链接是最佳解决方案？
Is there a better way to declare my function so that it does not throw this UncaughtReference error, or is keeping the Jquery link in the head the best solution?
推荐答案
这是因为你试图在 jQuery 这样的库
It is because you are trying to use jQuery before jQuery has been loaded. You need to put libs like jQuery in the head of your document
<head>
<link rel="stylesheet" type="text/css" href="css/bootstrap.css" />
<script type="text/javascript" src="js/jquery.min.js"></script>
<script type="text/javascript" src="js/bootstrap.js"></script>
</head>
一般来说，你的脚本会在文档的末尾靠近close主体标记和库等文库你正在使用去< head>
Generally your scripts go at the end of the document near the close body tag and libraries such as the ones you are using go at the <head>
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