This command is a personal favorite of mine, not just because it's uniquely useful but because it was the first major piece of code that I wrote in the binary all by my lonesome. :-)
This SSJS filter gives you a real-time hook into any change of a user record, in much the same way that the *editFilterPre and -Post give you a real-time hook into changes of nodes in the folder/discussion/message hierarchy. When is this useful? Well, originally it was implemented to keep an external authentication database in sync with Webcrossing's database. For various reasons the client needed to be able to change user data from either direction so we wrote this filter so that it would fire whenever a user changed any field in their preferences or any other field in the user record was changed by a system process.
The filter also proved useful in a realtime forensics situation where a client suspected unauthorized access; with a userChangeFilterPost filter configured to send alerts it was possible to watch events as they unfolded rather than spelunking the logs afterwards.
The filter works simply: when it fires, two special globals are defined: changedUserId is the userId that was changed and changedFieldName is the name of the property that was altered; that includes both the built-in and custom properties. So the basic syntax is
var theUser = User.open(changedUserId);
theUser[changedFieldName]
to access the altered property. (Note the brackets syntax; theUser.changedFieldName treats the variable as a string literal which is not what you want.)
Like always, the User.open should be inside a try/catch structure because if the user has been deleted by some other process, it will throw an exception and halt processing.
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