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What is Ajax?
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Ajax is Asynchronous JavaScript and XML .It enables the programmer to execute a server-side script without refreshing the page. |
A scripting technique for silently loading new data from the server. Although AJAX scripts commonly use the soon to be standardized XMLHttpRequest object, they could also use a hidden iframe or frame. An AJAX script is useless by itself. It also requires a DOM Scripting component to embed the received data in the document.
Asynchronous JavaScript and XML (AJAX) is not a technology in itself, but is a term that describes a "new" approach to using a number of existing technologies together, including: HTML or XHTML, Cascading Style Sheets, JavaScript, The Document Object Model, XML, XSLT, and the XMLHttpRequest object. When these technologies are combined in the AJAX model, web applications are able to make quick, incremental updates to the user interface without reloading the entire browser page. This makes the application faster and more responsive to user actions.
How does AJAX work?
The core idea behind AJAX is to make the communication with the server asynchronous, so that data is transferred and processed in the background. As a result the user can continue working on the other parts of the page without interruption. In an AJAX-enabled application only the relevant page elements are updated, only when this is necessary.The following diagram will explain the life cycle of Ajax enabled system
- Initial request by the browser – the user requests the particular URL.
- The complete page is rendered by the server (along with the JavaScript AJAX engine) and sent to the client (HTML, CSS, JavaScript AJAX engine).
- All subsequent requests to the server are initiated as function calls to the JavaScript engine.
- The JavaScript engine then makes an XmlHttpRequest to the server.
- The server processes the request and sends a response in XML format to the client (XML document). It contains the data only of the page elements that need to be changed. In most cases this data comprises just a fraction of the total page markup.
- The AJAX engine processes the server response, updates the relevant page content or performs another operation with the new data received from the server. (HTML + CSS)
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