Allerson Allerson - 1 month ago 17
Javascript Question

How to force refresh client js from server side?

Here is the case:

I get a js to monitor web ads.Because of the browser cache,when i update js on server side,js on client side will not be refreshed immediately.How could i force refresh client js as soon as i update js on server side?

p.s. Add version number strategy is not useful in my case.

Answer

You can use HTTP's cache-control mechanisms to control the browser's caching.

When serving a copy of your JS file, include an ETag and/or Last-Modified header in the response. Also include a "Cache-Control: must-revalidate" header. This tells the browser that it must check back with the server every time, and it can send an If-None-Match and/or If-Modified-Since header in future requests to ask the server to send the file only if it's changed.

If you'd like to avoid the load of browsers checking with the server every time, and it's OK for the changes to not take effect immediately, you can also include a Date header with the current time and an Expires header set to some point in the future — maybe 12 or 24 hours. That allows the browser to use its cached copy for the specified amount of time before it has to check back with your server again.

HTTP's cache-control features are pretty robust, but there are plenty of nuances, such as controls for intermediate caches (e.g. other systems between your server and the user's browser). You'll want to read about caching in HTTP overall, not just the specific header fields that I've mentioned.