jQuery CDN is not loading on LocalHost

I have a jquery cdn loading from the following:

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>

then in the body I have my source for my script

.<script src="app.js"></script>

This is all on local, but when I view in browser I keep getting the following errors in console:

GET file://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js
Uncaught ReferenceError: $ is not defined 

I assume this is saying the jQuery function "$..." is undefined because there is an error in GET of the CDN, why would this be happening on local?



You aren't actually running on localhost (http://localhost) but on the local file system (file:///path/to/whatever.html). The protocol is copied with the // link to file://ajax.googleapis.com which of course doesn't exist.

You should set up a server on your computer so that you'd have an actual localhost accessed with the http protocol. It would have other benefits as well since browsers act a bit differently also in other regards when the page is loaded directly from the file system.


Have you tried removing the "//" at the beginning of the "src" attribute and instead using "http://"? It is probably appending "localhost" to the beginning of the URL because of those slashes.


I've answered a similar question in How to use Bootstrap CDN? and, as Juhana said, the problem is the missing protocol when loading jQuery.

The protocol-less CDN works when you are using http or https, because browsers will add the prefix to the jQuery URL with it.

But when using a local html file, the missing protocol will be file: and browsers will not be able to find jQuery in something like file://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js failing to load it. In that case you must add the protocol manually, which is a pitty if you finally use the page on-line because a protocol-less URL is better and more cache friendly (http://encosia.com/cripple-the-google-cdns-caching-with-a-single-character/).


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