1. The user performs an action on the browser, for example, pressing a button or typing in text, and triggers a
JavaScript function.
2. In the background, the AJAX engine sends an http request to the server. As soon as the AJAX engine
makes the request, the JavaScript call is transmitted back to the caller. This is termed asynchronous
communication. When the AJAX engine receives the http response from the server, the AJAX engine will
directly call the corresponding function to notify the browser, which produces a reaction on the user interface [7,
8]. A detailed comparison is shown in Fig. 3 and 4.