Ajax (programming) - Revision history

Shawndouglas: Internal links

2014-08-22T17:03:17Z

Internal links

← Older revision		Revision as of 17:03, 22 August 2014
Line 1:		Line 1:
	'''Ajax''' (also '''AJAX''') is a group of interrelated Web development techniques used on the client-side to create asynchronous Web applications. With Ajax, Web applications can send data to and retrieve data from a server asynchronously (in the background) without interfering with the display and behavior of the existing page. Data can be retrieved using the XMLHttpRequest object and API (application programming interface). Despite the name, the use of XML is not required; JavaScript Object Notation (JSON) is often used instead, and the requests do not need to be asynchronous.<ref name="UllmanWrox">{{cite book		'''Ajax''' (also '''AJAX''') is a group of interrelated Web development techniques used on the client-side to create asynchronous Web applications. With Ajax, Web applications can send data to and retrieve data from a server asynchronously (in the background) without interfering with the display and behavior of the existing page. Data can be retrieved using the XMLHttpRequest object and API (application programming interface). Despite the name, the use of [[XML]] is not required; [[JSON\|JavaScript Object Notation]] (JSON) is often used instead, and the requests do not need to be asynchronous.<ref name="UllmanWrox">{{cite book
	\|url=http://www.wrox.com/WileyCDA/Section/id-303217.html \|archiveurl=https://web.archive.org/web/20080705101852/http://www.wrox.com/WileyCDA/Section/id-303217.html \|title=Beginning Ajax \|author=Ullman, Chris \|publisher=Wrox \|date=March 2007 \|isbn=9780470106754 \|archivedate=05 July 2008 \|accessdate=18 August 2014}}</ref>		\|url=http://www.wrox.com/WileyCDA/Section/id-303217.html \|archiveurl=https://web.archive.org/web/20080705101852/http://www.wrox.com/WileyCDA/Section/id-303217.html \|title=Beginning Ajax \|author=Ullman, Chris \|publisher=Wrox \|date=March 2007 \|isbn=9780470106754 \|archivedate=05 July 2008 \|accessdate=18 August 2014}}</ref>

Shawndouglas: /* References */ Updated cat.

2014-08-22T16:20:51Z

References: Updated cat.

← Older revision		Revision as of 16:20, 22 August 2014
Line 54:		Line 54:

	<!---Place all category tags here-->		<!---Place all category tags here-->
	[[Category:Software terms]]		[[Category:Software and hardware terms]]

Shawndouglas: /* References */ Added cat

2014-08-22T16:13:29Z

References: Added cat

← Older revision		Revision as of 16:13, 22 August 2014
Line 52:		Line 52:
	==References==		==References==
	<references />		<references />

			<!---Place all category tags here-->
			[[Category:Software terms]]

Shawndouglas: /* Technologies */ Punctuation

2014-08-19T01:01:14Z

Technologies: Punctuation

← Older revision		Revision as of 01:01, 19 August 2014
Line 13:		Line 13:

	==Technologies==		==Technologies==
	The term ''Ajax'' has come to represent a broad group of Web technologies that can be used to implement a Web application that communicates with a server in the background, without interfering with the current state of the page. In the article that coined the term "Ajax," Jesse James Garrett explained the incorporated technologies<ref name="APGarrett05" />:		The term "Ajax" has come to represent a broad group of Web technologies that can be used to implement a Web application that communicates with a server in the background, without interfering with the current state of the page. In the article that coined the term "Ajax," Jesse James Garrett explained the incorporated technologies<ref name="APGarrett05" />:
	* HTML (or XHTML) and CSS for presentation		* HTML (or XHTML) and CSS for presentation
	* The Document Object Model (DOM) for dynamic display of and interaction with data		* The Document Object Model (DOM) for dynamic display of and interaction with data

Shawndouglas: Added notes.

2014-08-18T23:59:36Z

Added notes.

← Older revision		Revision as of 23:59, 18 August 2014
Line 46:		Line 46:
	==External links==		==External links==
	* [http://www.xul.fr/en-xml-ajax.html Ajax Tutorial] with GET, POST, text and XML examples.		* [http://www.xul.fr/en-xml-ajax.html Ajax Tutorial] with GET, POST, text and XML examples.

			==Notes==
			Numerous elements of this article are reused from [http://en.wikipedia.org/wiki/Ajax_%28programming%29 the Wikipedia article].

	==References==		==References==
	<references />		<references />

Shawndouglas: Updated content.

2014-08-18T23:57:55Z

Updated content.

Show changes

Shawndouglas: Creating stub record. Saving and modifying more of its content.

2014-08-18T22:51:42Z

Creating stub record. Saving and modifying more of its content.

New page

'''Ajax''' (also '''AJAX''') is a group of interrelated Web development techniques used on the client-side to create asynchronous Web applications. With Ajax, Web applications can send data to and retrieve data from a server asynchronously (in the background) without interfering with the display and behavior of the existing page. Data can be retrieved using the XMLHttpRequest object and API (application programming interface). Despite the name, the use of XML is not required; JavaScript Object Notation (JSON) is often used instead, and the requests do not need to be asynchronous.<ref name="UllmanWrox">{{cite book
|url=http://www.wrox.com/WileyCDA/Section/id-303217.html |archiveurl=https://web.archive.org/web/20080705101852/http://www.wrox.com/WileyCDA/Section/id-303217.html |title=Beginning Ajax |author=Ullman, Chris |publisher=Wrox |date=March 2007 |isbn=9780470106754 |archivedate=05 July 2008 |accessdate=18 August 2014}}</ref>

Ajax is a group of technologies. HTML and CSS can be used in combination to mark up and style information. The Document Object Model (DOM) is 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 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. Later in the mid- to late '90s, Microsoft began updating its Internet Explorer browser to better handle content asynchronously, including the introduction of the <code>iframe</code> tag in 1996, the first XMLHTTP component in 1998, and an XMLHTTP ActiveX control in 1999 that years later was adopted by Mozilla, Safari, Opera, and other browsers as the XMLHttpRequest JavaScript object.<ref name="SwartzApple">{{cite web |url=http://developer.apple.com/internet/webcontent/xmlhttpreq.html |archiveurl=https://web.archive.org/web/20110305043442/http://developer.apple.com/internet/webcontent/xmlhttpreq.html |title=Dynamic HTML and XML: The XMLHttpRequest Object |publisher=Apple Inc |date=24 June 2014 |archivedate=05 March 2011 |accessdate=18 August 2014}}</ref>

By the mid-2000s, the idea of using XML within HTTP requests began to truly take shape. Microsoft had already worked on adding this sort of functionality into its Outlook Web Access for Exchange in the early 2000s, and Google followed suit with it Gmail and Google Maps products in 2004 and 2005 respectively.<ref name="OWA05">{{cite web |url=http://blogs.technet.com/b/exchange/archive/2005/06/21/406646.aspx |title=Outlook Web Access - A catalyst for web evolution |author=Microsoft Exchange Team |publisher=Microsoft |date=21 June 2005 |accessdate=18 August 2014}}</ref><ref name="SwarzAjax">{{cite web |url=http://www.aaronsw.com/weblog/ajaxhistory |title=A Brief History of Ajax |author=Swartz, Aaron |work=Raw Thought |date=22 December 2005 |accessdate=18 August 2014}}</ref><ref name="APGarrett05">{{cite web |url=http://www.adaptivepath.com/ideas/essays/archives/000385.php |archiveurl=https://web.archive.org/web/20080702075113/http://www.adaptivepath.com/ideas/essays/archives/000385.php |title=Ajax: A New Approach to Web Applications |author=Garrett, Jesse James |publisher=Adaptive Path |date=18 February 2005 |archivedate=02 July 2008 |accessdate=18 August 2014}}</ref> And in October 2004 the public beta release of Kayak.com was among the first large-scale e-commerce applications of the technology, what their developers at that time called "the xml http thing."<ref name="KayakDev06">{{cite web |url=http://kayaklabs.blogspot.com/2006/04/kayak-user-interface.html |title=Kayak User Interface |work=Official Kayak.com Technoblog |author=English, Paul |publisher=Kayak.com |date=12 April 2006 |accessdate=18 August 2014}}</ref> The set of technologies would formally stick with the name "Ajax," an acronym for "asynchronous JavaScript and XML," and be described by Adaptive Path's founder and president Jesse James Garrett in February 2005 as "several technologies, each flourishing in its own right, coming together in powerful new ways."<ref name="APGarrett05" /><ref name="UllmanWrox" />

On April 5, 2006, the World Wide Web Consortium (W3C) released the first draft specification for the Ajax XMLHttpRequest object in an attempt to create an official Web standard.<ref name="XHRStand">{{cite web
|url=http://www.w3.org/TR/2006/WD-XMLHttpRequest-20060405/ |archiveurl=https://web.archive.org/web/20080516060525/http://www.w3.org/TR/2006/WD-XMLHttpRequest-20060405/ |title=The XMLHttpRequest Object |publisher=World Wide Web Consortium |date=05 April 2006 |archivedate=16 May 2008 |accessdate=18 August 2014}}</ref> The standard was created, and as of August 2014 is still maintained by the W3C.<ref name="XHRLivingStand">{{cite web |url=http://xhr.spec.whatwg.org/ |title=XMLHttpRequest Living Standard |publisher=W3C |date=12 August 2014 |accessdate=18 August 2014}}</ref>

==Technologies==
The term ''Ajax'' has come to represent a broad group of Web technologies that can be used to implement a Web application that communicates with a server in the background, without interfering with the current state of the page. In the article that coined the term "Ajax," Jesse James Garrett explained that the following technologies are incorporated<ref name="APGarrett05" />:
* HTML (or XHTML) and CSS for presentation
* The Document Object Model (DOM) for dynamic display of and interaction with data
* XML for the interchange of data, and XSLT for its manipulation
* The XMLHttpRequest object for asynchronous communication
* JavaScript to bring these technologies together

Since then, however, there have been a number of developments in the technologies used in an Ajax application and the definition of the term Ajax. XML is not required for data interchange and XSLT is not required for the manipulation of data. |JavaScript Object Notation (JSON) is often used as an alternative format for data interchange,<ref name="tapestry">{{cite Web
| url=http://tapestry.apache.org/tapestry4.1/ajax/json.html
| title=JavaScript Object Notation
| publisher=Apache.org
| accessdate=4 July 2008
| archiveurl=https://Web.archive.org/Web/20080616113121/http://tapestry.apache.org/tapestry4.1/ajax/json.html
| archivedate=16 June 2008 
| deadurl=no}}</ref> although other formats such as preformatted HTML or plain text can also be used.<ref name="devx-json">{{cite Web
| url=http://www.devx.com/Webdev/Article/32651
| title=Speed Up Your Ajax-based Apps with JSON
| publisher=DevX.com
| accessdate=4 July 2008| archiveurl=https://Web.archive.org/Web/20080704134131/http://www.devx.com/Webdev/Article/32651
| archivedate=4 July 2008 
| deadurl=no}}</ref>

[http://microformats.org/wiki/rest/ahah Asynchronous HTML and HTTP] (AHAH) involves using XMLHTTPRequest to retrieve (X)HTML fragments, which are then inserted directly into the Web page.

== Drawbacks ==
* In pre-[[HTML5]] browsers, pages dynamically created using successive Ajax requests did not automatically register themselves with the browser's history engine, so clicking the browser's "back" button may not have returned the browser to an earlier state of the Ajax-enabled page, but may have instead returned to the last full page visited before it. Such behavior — navigating between pages instead of navigating between page states — may be desirable, but if fine-grained tracking of page state is required, then a pre-[[HTML5]] workaround was to use invisible iframes to trigger changes in the browser's history. A workaround implemented by Ajax techniques is to change the URL [[fragment identifier]] (the part of a URL after the "#") when an Ajax-enabled page is accessed and monitor it for changes.<ref name="interakt">{{cite web
| url=http://www.interaktonline.com/support/articles/Details/Ajax:+Asynchronously+Moving+Forward-Why+use+Ajax%3F.html?id_art=36&id_asc=309
| title=Why use Ajax?
| publisher=InterAKT
| date=10 November 2005
| accessdate=26 June 2008
| archiveurl=https://web.archive.org/web/20080529080808/http://www.interaktonline.com/support/articles/Details/AJAX:+Asynchronously+Moving+Forward-Why+use+AJAX%3F.html?id_art=36&id_asc=309
| archivedate=29 May 2008 
| deadurl=no}}</ref><ref name="deepLinkAjax">{{cite web
| url=http://blog.onthewings.net/2009/04/08/deep-linking-for-ajax/
| title=Deep Linking for AJAX}}</ref> [[HTML5]] provides an extensive [[API]] standard for working with the browser's history engine.<ref name="html5-1">{{Cite web
| url=http://www.whatwg.org/specs/web-apps/current-work/multipage/history.html|title=HTML5 specification
| accessdate=21 October 2011}}</ref>
* [[Dynamic web page|Dynamic Web page]] updates also make it difficult to [[Internet bookmark|bookmark]] and return to a particular state of the application. Solutions to this problem exist, many of which again use the URL fragment identifier.<ref name=interakt/><ref name=deepLinkAjax/> The solution provided by HTML5 for the above problem also applies for this.<ref name=html5-1/>
* Depending on the nature of the Ajax application, dynamic page updates may interfere disruptively with user interactions, especially if working on an unstable Internet connection. For instance, editing a search field may trigger a query to the server for search completions, but the user may not know that a search completion popup is forthcoming, and if the internet connection is slow, the popup list may show up at an inconvenient time, when the user has already proceeded to do something else.
* Most [[Web crawler]]s do not execute JavaScript code,<ref name="IBM">{{cite web
| url=http://www.ibm.com/developerworks/library/x-sitemaps/index.html
| title=Help Web crawlers efficiently crawl your portal sites and Web sites
| publisher=[[IBM]]
| first=Andreas
| last=Prokoph
| date=8 May 2007
| accessdate=22 April 2009}}</ref> so in order to be indexed by [[search engines]], a Web application must provide an alternative means of accessing the content that would normally be retrieved with Ajax.
* Any user whose browser does not support JavaScript or <code>XMLHttpRequest</code>, or simply has this functionality disabled, will not be able to properly use pages which depend on Ajax. Devices such as [[smartphone]]s and [[PDA]]s may not have support for the required technologies, though this is becoming less of a problem. The only way to let the user carry out functionality is to fall back to non-JavaScript methods. This can be achieved by making sure links and forms can be resolved properly and not relying solely on Ajax.<ref>{{cite web
| url=http://www.alistapart.com/articles/userproofingajax
| title=User-proofing Ajax
| first=Peter
| last=Quinsey}}</ref>
* Similarly, some Web applications that use Ajax are built in a way that cannot be read by screen-reading technologies, such as [[JAWS (screen reader)|JAWS]]. The [[WAI-ARIA]] standards provide a way to provide hints in such a case.<ref name="WAI_ARIA">{{cite web
| url=http://www.w3.org/WAI/intro/aria.php
| title=WAI-ARIA Overview
| publisher=http://www.w3.org/
| accessdate=21 October 2010
| archiveurl=https://web.archive.org/web/20101026062837/http://www.w3.org/WAI/intro/aria.php
| archivedate=26 October 2010 
| deadurl= no}}</ref>
* Screen readers that are able to use Ajax may still not be able to properly read the dynamically generated content.<ref name="sitepoint">{{cite web
| url=http://articles.sitepoint.com/article/ajax-screenreaders-work
| title=Ajax and Screenreaders: When Can it Work?
| publisher=[[sitepoint.com]]
| first=James
| last=Edwards
| date=5 May 2006
| accessdate=27 June 2008}}</ref>
* The [[same origin policy]] prevents some Ajax techniques from being used across domains,<ref name="xhr-standard" /> although the W3C has a draft of the XMLHttpRequest object that would enable this functionality.<ref name="xdr">{{cite web
| url=http://dev.w3.org/2006/waf/access-control/
| title=Access Control for Cross-Site Requests
| publisher=World Wide Web Consortium
| accessdate=27 June 2008
| archiveurl=https://web.archive.org/web/20080514034546/http://dev.w3.org/2006/waf/access-control/
| archivedate=14 May 2008 
| deadurl= no}}</ref> Methods exist to sidestep this security feature by using a special Cross Domain Communications channel embedded as an iframe within a page,<ref name="CrossDomainCommunication">{{cite web
| url=http://msdn.microsoft.com/en-us/library/bb735305.aspx
| title=Secure Cross-Domain Communication in the Browser
| publisher=The Architecture Journal (MSDN)
| accessdate=27 April 2010
| archiveurl=https://web.archive.org/web/20100329064533/http://msdn.microsoft.com/en-us/library/bb735305.aspx
| archivedate=29 March 2010 | deadurl= no}}</ref> or by the use of [[JSONP#JSONP|JSONP]].
* The asynchronous [[Callback (computer programming)|callback-style of programming]] required can lead to complex code that is hard to maintain, to debug<ref name="async_wrong">{{cite web
| url=http://gfxmonk.net/2010/07/04/defer-taming-asynchronous-javascript-with-coffeescript.html#1
| title=What is asynchronous programming, and why is it so damn awkward?
| publisher=http://gfxmonk.net/
| first=Tim
| last=Cuthbertson
| accessdate=19 October 2010}}
</ref> and to test.<ref name="selenium">{{cite web
| url=http://seleniumhq.org/docs/03_webdriver.html#fetching-a-page
| title=Selenium documentation: Fetching a Page
| publisher=http://seleniumhq.org/
| accessdate=6 October 2011 }}<br />It is worth noting that if your page uses a lot of Ajax on load then WebDriver may not know when it has completely loaded. If you need to ensure such pages are fully loaded, then you can use Explicit and Implicit Waits.</ref>

==External links==
* [http://www.adaptivepath.com/ideas/ajax-new-approach-web-applications/ Ajax: A New Approach to Web Applications] — Article that coined the AJAX term and Q&A
* {{dmoz|Computers/Programming/Languages/JavaScript/Ajax}}
* [http://www.xul.fr/en-xml-ajax.html Ajax Tutorial] with GET, POST, text and XML examples.

==References==
<references />