2. AJAX
AJAX stands for Asynchronous JavaScript and XML, and
is a web application that is responsible for such things as
the list of suggestions that drop down as you enter text
into a Google search box or the ability to zoom in and out
in Google Maps, all without reloading the entire page.
3. THE LITTLE ENGINE
AJAX utilizes several different web-based technologies
and standards to create an intermediary – an AJAX
engine – between the user and the server. While a user
browses a webpage, the AJAX engine communicates with
the server in the background, updating parts of the
webpage without interfering with the entire page and
making the user wait while it reloads.
An example is Gmail. An AJAX engine checks and adds
new mail as it comes in, without reloading the page.
4. AJAX: A NEW APPROACH TO WEB APPLICATIONS
―Ajax isn’t something you can download. It’s an
approach—a way of thinking about the architecture of
web applications using certain technologies.‖
-- Jesse James Garrett, Chief
Creative Officer of
AdaptivePath.com, and the man
generally considered to have
coined the term AJAX in 2005.
5. IN A NAME
AJAX refers to two technologies (JavaScript and XML)
and a technique (asynchronous) for loading information.
But it incorporates so much more.
6. TECHNOLOGIES
AJAX incorporates:
• XHTML and CSS are standard languages that browsers understand and are
used to present information to the user. XHTML for content and CSS for
layout and formatting.
• XML and XSLT describes information and distributes it in a platform-
independent format. XML is used for the interchange of data from a dynamic
data source, and XSLT to process and manipulate it for final output on the
webpage
• Document Object Model (DOM) allows programs to access and update the
content, structure and style of a document once it is displayed. This allows
the user to interact with the content presented, such as greying-out a button
once certain information is entered.
• Asynchronous -- being independent of communication with a server – data
retrieval using XMLHttpRequest is when a change is made to a page (the
user zooms in on a section of a map). Only the part of the webpage to
change is transferred from the server, and not the entire page
• JavaScript is the glue that holds all the elements together. JavaScript is a
programming language used to perform various tasks, and binds all the
AJAX technologies.
7. BROAD GROUP OF TECHNOLOGIES
AJAX applications can be any size, from the very
simple, single function application to the complex and
sophisticated. It also is constantly in development and
being refined to incorporate new applications or
technologies.
8. ADDING A LAYER
The basic building blocks of AJAX were introduced in the
1990s, when most websites were based on complete
HTML pages. Every user action on a webpage, required
the page to be re-loaded from the server – all the content
re-sent instead of only the changed information --
causing a start-stop-start-stop experience for the user.
11. THE AJAX ENGINE
Instead of loading a webpage, the browser loads an AJAX engine –
written in JavaScript and usually tucked away in a hidden frame. The
AJAX engine is responsible for both rendering the interface the user
sees and also communicating with the server on the user’s behalf.
With the AJAX engine, a webpage is loaded entirely only once. Every
user action takes the form of a JavaScript call to the AJAX engine. This
allows for the users interaction with the webpage to happen
asynchronously – independent of communication with the server –
keeping the user from having to stare at a spinning color wheel or
hourglass icon.
14. BUILDING BLOCKS
Asynchronous loading of content first became practical in 1995 when
Java applets were written into the first version of Java language. The
applets collect user data, such as mouse input, buttons and check
boxes, and load data asynchronously from the server after a page has
been loaded.
Internet Explorer introduced the iframe element to HTML in 1996, which
also enabled asynchronous loading. It took off in 1999, when Microsoft
used the iframe technology to update news stories and stock quotes on
the default page of Internet Explorer. That same year, Microsoft created
the XMLHTTP Active X control in Internet Explorer 5. The programing
was adopted by Mozilla, Safari and Opera as XMLHttpRequest
JavaScript, which is commonly used in today AJAX applications.
15. FULL SCALE ONLINE APPLICATION
In 2000, Microsoft filed a patent on the basic AJAX technology.
AJAX began to gain widespread use in 2000, when it was applied to
Outlook Web Access and then Oddpost in 2002. It became a web
standard in 2004 when Gmail adopted the application, and then in
2005, with Google Maps.
16. REFERENCES
• Ajax (programming) http://en.wikipedia.org/wiki/Ajax_(programming)
• Ajax: A New Approach to Web Applications
http://www.adaptivepath.com/ideas/ajax-new-approach-web-
applications
• Beginning Ajax http://www.wrox.com/WileyCDA/Section/What-is-Ajax-
.id-303217.html
• Why use Ajax?
http://www.interaktonline.com/support/articles/Details/AJAX%3A+Async
hronously+Moving+Forward-Introduction.html?id_art=36&id_asc=306
• A Brief History of Ajax http://www.aaronsw.com/weblog/ajaxhistory
Notes de l'éditeur
AJAX stands for Asynchronous JavaScript and XML, and is a web application that is responsible for such things as the list of suggestions that drop down as you enter text into a Google search box or the ability to zoom in and out in Google Maps, all without reloading the entire page.
AJAX applications can be any size, from the very simple, single function application to the complex and sophisticated. It also is constantly in development and being refined to incorporate new applications or technologies. For example, despite the XML in the AJAX name, it is not necessarily needed, and JavaScript Object Notation (JSON) is often used instead. In addition, VBScript can be used instead of JavaScript as a client-side scripting language in an AJAX application. The requests sent between the user and the server also do not have to be asynchronous for an AJAX engine to work. It all depends on the need and function of the page.
The AJAX model gives the user the feeling that changes are instantaneous and the user is much more responsive as only small parts of the page are transferred at a time.
User waiting time is reduced with the AJAX engine, only relevant content changes, as needed, and the user can still work within a page while the data is being submitted. If a section of a page encounters an error, no other sections of the page are affected, and the user will not lose any data.
