Is the server or the client in control in AJAX?

With AJAX the control can be more centralized in a server-side component or a mix of client-side and server-side controllers.

• Centralized server-side controller:In this type of architecture, the controller ensures that the data on the client and the server are synchronized.
• Client and server-side controllers:In this type of architecture the presentation related control, event processing, page manipulation, and rendering of model data is done through Javascript on the client side.
• The server-side: is responsible for business logic and pushing updated model data to the client.
• Both methods are viable depending on the kind of task. However, the centralized server side controller is preferred as in the other case (Client and server-side controllers) the server might not have the knowledge of the state of the client page.