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Here is a very simple example to illustrate my question using JQuery from a CDN to modify the page:
<html>
<body>
<p>Hello Dean!</p>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
<script>$("p").html("Hello, Gabe!")</script>
</body>
</html>
When you load this page with an internet connection, the page displays "Hello Gabe". When I then turn off the internet connection, the page displays "Hello Dean" with an error -- JQuery is not available.
My understanding is that CDNs have a long Cache-Control and Expire in the header response, which I understand to mean that the browser caches the file locally.
$ curl -s -D - https://cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.min.js | head
HTTP/1.1 200 OK
Server: cloudflare-nginx
Date: Fri, 17 Apr 2015 16:30:33 GMT
Content-Type: application/javascript
Transfer-Encoding: chunked
Connection: keep-alive
Last-Modified: Thu, 18 Dec 2014 17:00:38 GMT
Expires: Wed, 06 Apr 2016 16:30:33 GMT
Cache-Control: public, max-age=30672000
But this does not appear to be happening. Can someone please explain what is going on? Also -- how can I get the browser to use the copy of JQuery in the cache somewhere?
This question came up because we want to be using CDN's to serve external libraries, but also want to be able to develop the page offline -- like on an airplane.
I get similar behavior using Chrome and Firefox.
732
To ensure you see the latest version of a site you need to clear the cache memory. This is done by doing a force refresh by pressing both control and F5 buttons simultaneously on your keyboard (depending on your browser). Most times a simple force cache refresh won't work and you need to clear the cache by hand.
Caching is at the heart of content delivery network (CDN) services. Similar to how browser caching stores files on a hard drive, where they can be more rapidly accessed, a CDN moves your website content to powerful proxy servers optimized for accelerated content distribution.
There's nothing to deal with CDN. When then browser encounters a script tag, it will request it to the server, whether it's hosted on a CDN or on your server. If the browser previously loaded it, on the same address, the server tells whether it should be reloaded or not (sending 304 HTTP status code).
What you are probably looking for is to cache your application for offline use. It's possible with HTML5 cache manifest file. You need to create a file listing all files needed to be cached for explicit offline use
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