In some countries, google, hosted query might be banned we must want to prevent errors. The following code will check jQuery is loaded or not. It is not loaded than jQuery script will be loaded from our web server.
Example:
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width" />
<title>cdn down</title>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script>if(!window.jQuery) { document.write('<scriptsrc="~/Scripts/jquery.min.js"><\/script>'); }
</script>
<script type="text/javascript">
$(function () {
$("#test").click(function (event) {
alert("hellojQuery");
});
});
</script>
</head>
<body>
<div>
<button id="test">click me</button>
</div>
</body>
</html>
Output: