What is Ajax - Basics of Ajax

AJAX iFour Consultancy

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What is Ajax?  An Asynchronous JavaScript and XML  Technique for creating fast and dynamic web pages  It allows web pages to be updated asynchronously by exchanging small amounts of data

with the server behind the scenes  This means that it is possible to update parts of a web page without reloading the whole page  Classic web pages, (which do not use AJAX) must reload the entire page if the content should change  Examples of applications using AJAX: Google Maps, Gmail, YouTube, and Facebook

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Why use Ajax?  Client/Server Apps:  Dynamic data  Static forms, controls, code, etc  Efficient, but not flexible  Traditional Web Apps:  Dynamic data  Dynamic forms, controls, code, etc  Flexible, but inefficient, and noticeably slow  Ajax Apps:  Dynamic data  Static or dynamic forms, controls, code, etc  Best of both worlds

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Why use Ajax? 

Multithreaded data retrieval from Web servers    

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Pre-fetch data before needed Progress indicators Appearance of speed Avoids need for setTimeout()

Less bandwidth required; less server load  

Reload partial page, not entire page Load data only, not even partial page

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jQuery AJAX  JQuery is a great javascript tool which provides a rich set of AJAX methods to develop next

generation web application  All jQuery AJAX methods use the ajax() method, this method is mostly used for requests where the other methods cannot be used 

Syntax : • $.ajax({name:value, name:value, ... }) • The parameters specifies one or more name/value pairs for the AJAX request

 Possible names/values in the table below: • async : A Boolean value indicating whether the request should be handled asynchronous or

not. Default is true • beforeSend() : A function to run before the request is sent

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jQuery AJAX  cache : A Boolean value indicating whether the browser should cache the requested pages. Default

is true  contentType : The content type used when sending data to the server  context : Specifies the "this" value for all AJAX related callback functions  data : Specifies data to be sent to the server  dataType : The data type expected of the server response  complete(status) : A function to run when the request is finished (after success and error functions)  error(status,error) : A function to run if the request fails  success(result,status) : A function to be run when the request succeeds  url : Specifies the URL to send the request to. Default is the current page  type : Specifies the type of request. (GET or POST)

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Loading Simple Data

[selector].load( URL, [data], [callback] ); [selector].load( URL, [data], [callback] );

 Here is the simple syntax for load() method   

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[selector].load( URL , [data] , [callback] ); URL : The URL of the server-side resource to which the request is sent data : Represents an object whose properties are serialized into properly encoded parameters to be passed to the request. If specified, the request is made using the POST method. If omitted, the GET method is used callback : This function invoked after the response data has been loaded into the elements of the matched set 

The first parameter passed to this function is the response text received from the server and second parameter is the status code

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Getting JSON data  Here is the simple syntax for getJSON() method   

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[selector].getJSON( URL , [data] , [callback] ); URL : The URL of the server-side resource contacted via the GET method data : An object whose properties serve as the name/value pairs used to construct a query string to be appended to the URL, or a preformatted and encoded query string callback : A function invoked when the request completes. The data value resulting from digesting the response body as a JSON string is passed as the first parameter to this callback, and the status as the second

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jQuery AJAX Methods  Following are all important JQuery AJAX methods for programming • jQuery.ajax(options) : Load a remote page using an HTTP request.

• jQuery.ajaxSetup(options) : Setup global settings for AJAX requests.

• jQuery.get( url, [data], [callback], [type] ) : Load a remote page using an HTTP GET request.

• jQuery.post( url, [data], [callback], [type] ) : Load a remote page using an HTTP POST request.

• jQuery.getJSON( url, [data], [callback] ) : Load JSON data using an HTTP GET request.

• jQuery.getScript( url, [callback] ) : Loads and executes a JavaScript file using an HTTP GET

request.

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jQuery AJAX Methods • load( url, [data], [callback] ) : Load HTML from a remote file and inject it into the DOM • serialize( ) : Serializes a set of input elements into a string of data • serializeArray( ) : Serializes all forms and form elements like the .serialize() method but

returns a JSON data structure

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jQuery AJAX Events  You can call various JQuery methods during the life cycle of AJAX call progress. Based on

different events/stages following methods are available

• ajaxComplete( callback ) : Attach a function to be executed whenever an AJAX request completes • ajaxStart( callback ) : Attach a function to be executed whenever an AJAX request begins and • • • •

there is none already active ajaxError( callback ) : Attach a function to be executed whenever an AJAX request fails ajaxSend( callback ) : Attach a function to be executed before an AJAX request is sent ajaxStop( callback ) : Attach a function to be executed whenever all AJAX requests have ended ajaxSuccess( callback ) : Attach a function to be executed whenever an AJAX request completes successfully

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Thank You..

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