forAsynchronous JavaScriptand XML) [ 1 ]is a group of interrelated Web developmenttechniques used on the client-sideto create asynchronous Web applications. With Ajax, Web applications can send data to, and retrieve data from, a serverasynchronously (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; JSONis often used instead (see AJAJ), and the requests do not need to be asynchronous. [ 2 ] Ajax is not a single technology, but a group of technologies. HTMLand CSScan be used in combination to mark up and style information. The DOMis accessed with JavaScript to dynamically display, and 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 Websites were based on complete HTML pages. Each user action required that a complete page be loaded from the server. This process was inefficient, as reflected by the user experience: all page content disappeared, then reappeared. Each time the browser reloaded a page because of 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 iframetag was introduced by Internet Explorerto load or to fetch content asynchronously. In 1998, Microsoft Outlook Web Appteam implemented the first component XMLHTTPby client script. In 1999, Microsoft used its iframe technology to dynamically update the news stories and stock quotes on the default page for Internet Explorer, [ 3 ]and created the XMLHTTP ActiveXcontrol in Internet Explorer 5, which was later adopted by Mozilla, Safari, Operaand other browsers as the XMLHttpRequest JavaScriptobject. [ 4 ]Microsoft has adopted the native XMLHttpRequest model as of Internet Explorer 7, though the ActiveX version is still supported. The utility of background HTTPrequests to the server and asynchronous Web technologies remained fairly obscure until it started appearing in full scale online applications such as Outlook Web App (2000) [ 5 ]and Oddpost(2002). Googlemade a wide deployment of standards-compliant, cross browserAjax with Gmail(2004) and Google Maps(2005). [ 6 ] The term Ajax was publicly stated on 18 February 2005 by Jesse James Garrettin an article titled Ajax: A New Approach to Web Applications, based on techniques used on Google pages. [ 1 ] On 5 April 2006, the World Wide Web Consortium(W3C) released the first draft specification for the XMLHttpRequest object in an attempt to create an official Web standard. [ 6 ]
Posted on: Thu, 22 May 2014 08:50:16 +0000
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