Ajax: Caching Problem with Requests

Well I am back from getting married and I am done with writing Ajax in Action so I thought that I would fill in some spare time and talk about a simple fix for a common question I get via email and the forums almost daily.

The question: The Ajax request is grabbing the cached page from the previous request, how do I stop this from happening? Well I have seen some fancy approaches by people, but there is one easy solution that works: a random query string value appended to the request.

So how and why does this work. Well it simple terms, when the browser looks at the destination, if it has a match, then it uses the data it has. Now this is great for when you are going to a static website, but since we are looking for new data, it sucks. By appending a random value to our parameters that we are sending back, it forces the browser to say, "Stop the press! We got new info here! Lets go get the data!"

I use this on my projects since I know my users have a major history of caching pages, especially with my dynamic PDF reports. It is always safer to append a random item to the query then having to worry about cached information.

The random tidbit of information you will submit to the server can be a number (larger the better), random string, or a timestamp. I prefer using the timestamp!

Well I hope this solves the problem of cached responses with Ajax. Remember to add your random friend to your parameters!

Eric Pascarello