How can I force clients to refresh JavaScript files?

How can I force clients to refresh JavaScript files?

We are currently working in a private beta and so are still in the process of making fairly rapid changes, although obviously as usage is starting to ramp up, we will be slowing down this process. That being said, one issue we are running into is that after we push out an update with new JavaScript files, the client browsers still use the cached version of the file and they do not see the update. Obviously, on a support call, we can simply inform them to do a ctrlF5 refresh to ensure that they get the up-to-date files from the server, but it would be preferable to handle this before that time.
Our current thought is to simply attach a version number onto the name of the JavaScript files and then when changes are made, increment the version on the script and update all references. This definitely gets the job done, but updating the references on each release could get cumbersome.
As I’m sure we’re not the first ones to deal with this, I figured I would throw it out to the community. How are you ensuring clients update their cache when you update your code? If you’re using the method described above, are you using a process that simplifies the change?

Solutions/Answers:

Solution 1:

As far as I know a common solution is to add a ?<version> to the script’s src link.

For instance:

<script type="text/javascript" src="myfile.js?1500"></script>

I assume at this point that there isn’t a better way than find-replace to increment these “version numbers” in all of the script tags?

You might have a version control system do that for you? Most version control systems have a way to automatically inject the revision number on check-in for instance.

It would look something like this:

<script type="text/javascript" src="myfile.js?$$REVISION$$"></script>

Of course, there are always better solutions like this one.

Solution 2:

Appending the current time to the URL is indeed a common solution. However, you can also manage this at the web server level, if you want to. The server can be configured to send different HTTP headers for javascript files.

For example, to force the file to be cached for no longer than 1 day, you would send:

Cache-Control: max-age=86400, must-revalidate

For beta, if you want to force the user to always get the latest, you would use:

Cache-Control: no-cache, must-revalidate

Solution 3:

Google Page-Speed: Don’t include a query string in the URL for static resources.
Most proxies, most notably Squid up through version 3.0, do not cache resources with a “?” in their URL even if a Cache-control: public header is present in the response. To enable proxy caching for these resources, remove query strings from references to static resources, and instead encode the parameters into the file names themselves.

In this case, you can include the version into URL ex: http://abc.com/v1.2/script.js and use apache mod_rewrite to redirect the link to http://abc.com/script.js. When you change the version, client browser will update the new file.

Solution 4:

This usage has been deprected:
https://developer.mozilla.org/en-US/docs/Web/HTML/Using_the_application_cache

This answer is only 6 years late, but I don’t see this answer in many places… HTML5 has introduced Application Cache which is used to solve this problem. I was finding that new server code I was writing was crashing old javascript stored in people’s browsers, so I wanted to find a way to expire their javascript. Use a manifest file that looks like this:

CACHE MANIFEST
# Aug 14, 2014
/mycode.js

NETWORK:
*

and generate this file with a new time stamp every time you want users to update their cache. As a side note, if you add this, the browser will not reload (even when a user refreshes the page) until the manifest tells it to.

Solution 5:

How about adding the filesize as a load parameter?

<script type='text/javascript' src='path/to/file/mylibrary.js?filever=<?=filesize('path/to/file/mylibrary.js')?>'></script>

So every time you update the file the “filever” parameter changes.

How about when you update the file and your update results in the same file size? what are the odds?

Solution 6:

Not all browsers cache files with ‘?’ in it. What I did to make sure it was cached as much as possible, I included the version in the filename.

So instead of stuff.js?123, I did stuff_123.js

I used mod_redirect(I think) in apache to to have stuff_*.js to go stuff.js