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Ajax (also AJAX ; short for "asynchronous JavaScript and XML") is a set of web development techniques that uses various web technologies on the client-side to create asynchronous . With Ajax, web applications can send and retrieve data from a Web server asynchronously (in the background) without interfering with the display and behaviour of the existing page. By decoupling the data exchange layer from the presentation layer, Ajax allows web pages and, by extension, web applications, to change content dynamically without the need to reload the entire page. In practice, modern implementations commonly utilize JSON instead of XML.
Ajax is not a technology, but rather a programming pattern. HTML and CSS can be used in combination to mark up and style information. The webpage can be modified by JavaScript to dynamically display (and allow the user to interact with) the new information. The built-in XMLHttpRequest object is used to execute Ajax on webpages, allowing websites to load content onto the screen without refreshing the page. Ajax is not a new technology, nor is it a new language. Instead, it is existing technologies used in a new way.
In 1996, the iframe tag was introduced by Internet Explorer; it can load a part of the web page asynchronously. In 1998, the Microsoft Outlook Web Access team developed the concept behind the XMLHttpRequest scripting object. It appeared as XMLHTTP in the second version of the MSXML library, which shipped with Internet Explorer 5.0 in March 1999.
The functionality of the Windows XMLHTTP ActiveX control in IE 5 was later implemented by Firefox, Safari, Opera, Google Chrome, and other browsers as the XMLHttpRequest JavaScript object. Microsoft adopted the native XMLHttpRequest model as of Internet Explorer 7. The ActiveX version is still supported in Internet Explorer and on "Internet Explorer mode" in Microsoft Edge. The utility of these background HTTP requests and asynchronous Web technologies remained fairly obscure until it started appearing in large scale online applications such as Outlook Web Access (2000) and Oddpost (2002).
Google made a wide deployment of standards-compliant, cross browser Ajax with Gmail (2004) and Google Maps (2005). In October 2004 Kayak.com's public beta release was among the first large-scale e-commerce uses of what their developers at that time called "the xml http thing". This increased interest in Ajax among web program developers.
The term AJAX was publicly used on 18 February 2005 by Jesse James Garrett in an article titled Ajax: A New Approach to Web Applications, based on techniques used on Google pages.
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. The latest draft of the XMLHttpRequest object was published on 6 October 2016, and the XMLHttpRequest specification is now a living document.
Since then, however, there have been a number of developments in the technologies used in an Ajax application, and in the definition of the term Ajax itself. XML is no longer required for data interchange and, therefore, XSLT is no longer required for the manipulation of data. JSON (JSON) is often used as an alternative format for data interchange, although other formats such as preformatted HTML or plain text can also be used. A variety of popular JavaScript libraries, including jQuery, include abstractions to assist in executing Ajax requests.
get-ajax-data.js:
// Initialize the HTTP request.
let xhr = new XMLHttpRequest();
// define the request
xhr.open('GET', 'send-ajax-data.php');
// Track the state changes of the request.
xhr.onreadystatechange = function ()
{
// Send the request to send-ajax-data.php
xhr.send(null);
const DONE = 4; // readyState 4 means the request is done.
const OK = 200; // status 200 is a successful return.
if (xhr.readyState === DONE)
{
if (xhr.status === OK)
{
console.log(xhr.responseText); // 'This is the output.'
}
else
{
console.log('Error: ' + xhr.status); // An error occurred during the request.
}
}
};
send-ajax-data.php:
// Send the data back.
echo "This is the output.";
?>
.then(data => console.log(data))
.catch (error => console.log('Error:' + error));
async function doAjax1() {
try
{
const res = await fetch('send-ajax-data.php');
const data = await res.text();
console.log(data);
}
catch (error)
{
console.log('Error:' + error);
}
}
doAjax1();
Fetch relies on JavaScript promises.
The fetch specification differs from Ajax in the following significant ways:
Furthermore, Ajax facilitates asynchronous processing by simplifying the utilization of XmlHttpRequest, which enables efficient handling of requests for asynchronous data retrieval. Additionally, the dynamic loading of content enhances the application's performance significantly.
Besides, Ajax enjoys broad support across all major web browsers, including Microsoft Internet Explorer versions 5 and above, Mozilla Firefox versions 1.0 and beyond, Opera versions 7.6 and above, and Apple Safari versions 1.2 and higher.
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