AJAX (Programming)

Ajax is a group of interrelated web development techniques used on the client-side to create asynchronous web applications. With Ajax, web applications can send data to, and retrieve data from, a server asynchronously (in the background) without interfering with the display and behavior of the existing page. Data can be retrieved using the XMLHttpRequest object. Despite the name, the use of XML is not required (JSON is often used instead), and the requests do not need to bisynchronous.

Ajax is not a single technology, but a group of technologies. HTML and CSS can be used in combination to mark up and style information. The DOM is accessed with JavaScript to dynamically display, and to allow the user to interact with the information presented. JavaScript and the XMLHttpRequest object provide a method for exchanging data asynchronously between browser and server to avoid full page reloads.

History

In the 1990s, most web sites were based on complete HTML pages. Each user action required that the page be reloaded from the server (or a new page loaded). This process was inefficient, as reflected by the user experience: all page content disappeared then reappeared. Each time a page was reloaded due to a partial change, all of the content had to be re-sent, even though only some of the information had changed. This placed additional load on the server and used excessive bandwidth.

In 1996, the iframe tag was introduced by Internet Explorer to load content asynchronously.

 

Technologies

The term Ajax has come to represent a broad group of web technologies that can be used to implement a web application that communicates with a server in the background, without interfering with the current state of the page. In the article that coined the term Ajax, [1] Jesse James Garrett explained that the following technologies are incorporated:

HTML (or XHTML) and CSS for presentation

The Document Object Model (DOM) for dynamic display of and interaction with data

XML for the interchange of data, and XSLT for its manipulation

The XMLHttpRequest object for asynchronous communication

JavaScript to bring these technologies together

Since then, however, there have been a number of developments in the technologies used in an Ajax application, and the definition of the term Ajax. XML is not required for data interchange and therefore XSLT is not required for the manipulation of data. JavaScript Object Notation (JSON) is often used as an alternative format for data interchange, [7] although other formats such as preformatted HTML or plain text can also be used.

 

 

How Ajax is Different

An Ajax application eliminates the start-stop-start-stop nature of interaction on the Web by introducing an intermediary—an Ajax engine—between the user and the server. It seems like adding a layer to the application would make it less responsive, but the opposite is true.

Instead of loading a webpage, at the start of the session, the browser loads an Ajax engine—written in JavaScript and usually tucked away in a hidden frame. This engine is responsible for both rendering the interface the user sees and communicating with the server on the user’s behalf. The Ajax engine allows the user’s interaction with the application to happen asynchronously—independent of communication with the server. So the user is never staring at a blank browser window and an hourglass icon, waiting around for the server to do something.

 

Artice By:

Priyanka Soni

Priyanka Rathod

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Comments
One Response to “AJAX (Programming)”
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