How can I force clients to refresh JavaScript files?

Question

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?

Answer 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> 

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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> 

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

Answer 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