How can I force clients to refresh JavaScript file

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

My colleague just found a reference to that method right after I posted (in reference to css) at http://www.stefanhayden.com/blog/2006/04/03/css-caching-hack/. Good to see that others are using it and it seems to work. 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?

Answer 2

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.

Answer 3

For ASP.NET pages I am using the following

BEFORE

<script src="/Scripts/pages/common.js" type="text/javascript"></script>

AFTER (force reload)

<script src="/Scripts/pages/common.js?ver<%=DateTime.Now.Ticks.ToString()%>" type="text/javascript"></script>

Adding the DateTime.Now.Ticks works very well.

Answer 4

Cache Busting in ASP.NET Core via a tag helper will handle this for you and allow your browser to keep cached scripts/css until the file changes. Simply add the tag helper asp-append-version="true" to your script (js) or link (css) tag:

<link rel="stylesheet" href="~/css/site.min.css" asp-append-version="true"/>

Dave Paquette has a good example and explanation of cache busting here (bottom of page) Cache Busting

Answer 5

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

Answer 6

If you're generating the page that links to the JS files a simple solution is appending the file's last modification timestamp to the generated links.

This is very similar to Huppie's answer, but works in version control systems without keyword substitution. It's also better than append the current time, since that would prevent caching even when the file didn't change at all.