AJAX Introduction

What is AJAX?

The acronym AJAX stands for Asynchronous JavaScript and XML.

  • It is usually a combination of several technologies such as HTML, JavaScript, The DOM and the XMLHttpRequest object (an object that lets you make requests to a server).
  • AJAX allows you make web based user interfaces more responsive and rich by letting you update specific part of the page without refreshing the entire page.
  • Conventional web application trasmit information to and from the sever using synchronous requests. This means you fill out a form, hit submit, and get directed to a new page with new information from the server.
  • With AJAX when submit is pressed, JavaScript will make a request to the server, process the results and update the current page. The user will never know that anything was even sent to the server.
  • XML is commonly used as the format for receiving server data, although any format, including plain text, can be used.
  • AJAX is a web browser technology independent of web server software.
  • A user can continue to use the application while the client program requests information from the server behind the scenes

How AJAX Works

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AJAX is based on the following open standards

  • Browser-based presentation using HTML and Cascading Style Sheets (CSS)
  • Data stored in XML format and fetched from the server
  • Behind-the-scenes data fetches using XMLHttpRequest objects in the browser
  • JavaScript to make everything happen

AJAX – Recommended Prerequisites

It is recommended that you are familiar with following before attempting this tutorial.

  • Basic HTML Concepts (GET requests/URL parameters)
  • Basic Javascript Concepts
  • The <div> tag