Ajax is a fairly broad technology with so many different client side and server side approaches that it’s hard to provide generic best practice rules. This however is one.

Requests via ajax tend to be handled asynchronously these days, communicating with the server whilst keeping the user interface active and responsive. This approach provides a potential problem though as it is possible to make a request and not worry about results, presuming what was sent just worked.

Better practice is to always respond from the server and at least have some form of simple logging at the client side so you can be certain communication is working as expected. It is simple for the server to respond with JSON in the form of:

{success:1}

This provides several pieces of information. Firstly the server action completed and was not met with an error such as error 500 (server error) or error 404 (page not found). Also if we toggle the “success” value with true or false, depending on the success of the request, we know that the process we requested was successful or failed. In one small line we rule out several potential points of failure.

Note that most major JavaScript libraries provide a simple means of handling success and failure so this is not hard to implement. In the case of Prototype you need only look at the “onError” and “onSuccess” attributes when defining the initial Ajax request.