Prototype Support for AJAX:

Prototype framework enables you to deal with Ajax calls in a very easy and fun way that is also safe (cross-browser). Prototype also deals in a smart way with JavaScript code returned from a server and provides helper classes for polling.

Ajax functionality is contained in the global Ajax object. This object provides all the necessary methods to handle AJAX requests and responses in an easy way:

AJAX Request: Actual requests are made by creating instances of the Ajax.Request() object.
new Ajax.Request('/some_url', { method:'get' });
The first parameter is the URL of the request; the second is the options hash. The method option refers to the HTTP method to be used; default method is POST

AJAX response callbacks: Ajax requests are by default asynchronous, which means you must have callbacks that will handle the data from a response. Callback methods are passed in the options hash when making a request:
new Ajax.Request('/some_url',
{
method:'get',
onSuccess: function(transport){
var response = transport.responseText || "no response text";
alert("Success! \n\n" + response);
},
onFailure: function(){ alert('Something went wrong...') }
});
Here, two callbacks are passed in the hash:
* onSuccess
* onFailure

Any of the above two call is called accordingly based on the status of the response. The first parameter passed to both is the native xmlHttpRequest object from which you can use its responseText and responseXML properties, respectively.

You can specify both callbacks, one or none - it's up to you. Other available callbacks are:
* onUninitialized
* onLoading
* onLoaded
* onInteractive
* onComplete
* onException
They all match a certain state of the xmlHttpRequest transport, except for onException which fires when there was an exception while dispatching other callbacks.
NOTE: The onUninitialized, onLoading, onLoaded, and onInteractive callbacks are not implemented consistently by all browsers. In general, it's best to avoid using these.

Prototype AJAX Methods :
Ajax object provides all the necessary methods to handle AJAX requests and responses in an easy way. Complete list of all the methods related to AJAX:

Methods	Description
Ajax Options	This is not a method but details all core options shared by all AJAX requesters and callbacks.
Ajax.PeriodicalUpdater()	Periodically performs an AJAX request and updates a container's contents based on the response text.
Ajax.Request()	Initiates and processes an AJAX request.
Ajax.Responders()	A repository of global listeners notified about every step of Prototype-based AJAX requests.
Ajax.Response()	The object passed as the first argument of all Ajax requests callbacks.
Ajax.Updater()	Performs an AJAX request and updates a container's contents based on the response text.