I have been updating a bunch of code recently to make use of the new features in Prototype 1.6 and one of the great additions in this release was the introduction of Automatic JavaScript response evaluation. This allowed me to improve on my session checking code without having to fuff around with the response information sent back to the client. The problem was with XHR requests: i.e. if the user initiated such a request when his session had expired, then usually the response would fail or worse just hang. The snippet below shows my new session checking code. [javascript] [/javascript] The trick is to intercept the call when you do your session checking at the back end. Let’s say you have a fuseaction called login.login (see below and yes this is fusebox 3 :S) where you display the login form when a user is not logged in, this is where I inserted the check for an XHR request, by looking at the http headers sent along with the request. The key here is a new header attribute passed in with Prototype “X-Requested-With”. If this attribute exists then I know it’s an XHR request and I can create a custom JSON header with an error struct that holds a key called session with a value of timeout. All I then need to do is encode the struct as JSON and pass that encoded struct back to the browser. [code] xfa.submitform=’index.cfm?fuseaction=login.processlogin’; [/code] Now let’s jump back to the JavaScript code and take a look at the onComplete function again: [javascript] onComplete : function(transport,json) { if(json && json[‘session’]) { setSessionExpired(); } else { //Code to run when the request has completed } } [/javascript] If there’s a JSON object and it has a key of session then I call my setSessionExpired function which redirects the users. Now the json session key only exists in these situations since the call normally just passes back the result of the call.