How can I decide if a website is using Ajax technology? What are the characteristics that I should I look in the website to tell it is an ajax application?
Search the javascript for XMLHttpRequest. Beyond that, the working definition of Ajax is rather too broad to look for, say, specific behaviours.
You can just look into the javascript source code and search for .ajax, .post and .get . If you find any of these they use ajax technologies.
You can also look at the network requests a page sends, if the page sends requests after loading the full page without you seeing it refreshing it probably uses ajax.
There's nothing special about websites using AJAX, it just means they make an asynchronous call to the server at some point. You can't know for certain that the website will make such a call unless you run it.
I am planning to develop a project which will have access to different services placed in different domains using ajax, so that it may get different types of data from each of them.
At the beginning I thought that due to cross-site scripting that can't be done so I would have to use a different approach or maybe use a bridge (make the calls to my server which will behind the scenes call the others) but the bridge would become a performance issue.
But then I was testing Angular using Google's API and realized that it just works. I mean, I could make AJAX calls to my localhost (though I know localhost may work just because it's localhost) using a script loaded from googleapis.com.
Now I wonder if it is possible or not to have a page with ajax calls to other domains like: mail.mydomain.com, profiles.mydomain.com, media.mydomain.com, and so on. And if so, can that be done just like that or are there any limitations? Because I remember that some years ago I had trouble doing things like that due to the cross-script block.
Just in case it helps, I'm planning to use Angular to get the data and paint it over the views.
Thanks.
Use JSON-P for cross domain AJAX. http://json-p.org/
Yes, it has limitations, but can be relieved easily.
Set HTTP header "Access-Control-Allow-Origin" to "*" does it.
I need to display some data(some text message) from a URL*(an HTML file)* which is in a different domain. I thought about using an iFrame to display the markup. Now the problem could be
if that site is down, then I wil see 404 error in that iFrame. i want to avoid that. I thought about using dojo to make an AJAX call to that URL to get the response, use innerHTML
to insert the response to the DOM. This is all what I need. But due to cross domain AJAX issues, I don't think it is possible. We are using dojo in our application. I searched
in Google to find a good implementation of Cross Domain scripting using Dojo. All I found is stuffs like JSONP. I don't want to make the remote domain return a JSONP. It is
just an HTML file and that file contains the markup that I need to print to the console. Can someone suggest a good way to do this.
Sadly as was already mentioned by Nakul in the comments, the same-origin policy does not allow for cross-domain XHR requests (at least in a cross-browser way).
The workarounds involve either cooperation from the cross-domain site (JSONP, CORS, various iframe communication tricks) or setting up a proxy in your own server so that all "cross-domain" go through your own domain first.
Facebook is doing Ajax History (Back and Forward button) and Bookmark using #! instead of just # in the URL. Is it always a good idea to do that, because I was thinking that a usual anchor could interfere with the Ajax History mechanism to trigger it into processing a normal anchor.
So, the Ajax History function will only process a hash portion only when it sees #! instead of just #.
And is using ! compatible with major browsers? If Facebook is using !, a guess is that it may be fairly well supported.
See Google's Making AJAX Applications Crawlable
for a possible use case (don't know if this is why Facebook used this fragment).
Update: This answer has been superseeded by this article. It discusses the issues with the Hashbang (#!), Hashes (#) and the HTML5 History API (pushState, popState) and the solutions.
In regards to usability on your website, it doesn't matter and you can use anything you like.
In regards to search engine optimization, having it and not having it both provide different avenues to go down.
For instance, Facebook uses the ! according to the Google Proposal for Making Ajax Applications Crawlable. Adding the ! will tell google that it should listen in on that ajax request and add that url to search engine results. This is great for websites which have already implemented ajax, as all you need to do is add the !.
The downside of this is that it only solves the problem of making your ajax crawlable. It does not solve the problems of:
Keeping the URLs clean and consistent for Ajax and Non-Ajax users. Eg. you could end up with www.facebook.com/profile.php?pid=123#!profile.php?pid=123
Keeping the website accessible by Non-Ajax users.
Keeping the URLs the same for both Ajax and Non-Ajax users.
Requires some severely complicated server side changes for escaping and translation of states in regards to query strings.
It is not compatible with the new HTML5 PopState functionality which is designed to truly solve these problems.
For websites which don't currently use ajax for everything, due to the problems above it is far better NOT using the Google Proposal as it is only workaround for sites like facebook which went ajax crazy and needed a desperate solution to SEO. There are alternatives which solve more of these problems (and with the HTML5 PopState now available can solve all the problems). One such alternative is jQuery Ajaxy (as seen on balupton.com) which works by simply upgrading your website into a ajax application, while keeping the experience for a Ajax-Enabled rich and interactive and continuing to work perfectly for Ajax-Disabled users.
I have to start using AJAX in a project and I don't know where to start. Can someone please help?
Asynchronous JavaScript And Xml. A technique for achieving bi-directional, script-driven communications between Web browsers and servers via HTTP.
See also:
definition on Wikipedia
AJAX Introduction on w3schools
Ajax Workshop 1 on Ajax Lessons
Edit: As pointed out by Nosredna, JSON is often used in place of XML.
The rough idea in English:
You have a web page. Some event (can be a button press or other form event, or just something triggered by a timer) occurs and triggers JavaScript code that asks the server for fresh information (like the latest value of GOOG stock).
There's a piece of code on the server that collects the info you passed and sends some info back. That's different from the page-serving job the server usually has.
When the server answers, a callback function (that you specified in the JavaScript call to the server) is called with the info from the server. Your JavaScript code uses the info to update something--like a GOOG stock chart.
Not to be confused with the cleaner, AJAX, the technology term, is really describing a framework or better stated as a technique for using XML and JavaScript to make asynchronous calls to server side code...
Here are some good code samples. And some more.
While many of these samples above show how to create all of the XML Request objects, if you look into the AJAX Control Toolkit from Microsoft for ASP.NET applications or jQuery, you'll find these easier to work with.
jQuery Sample (from jQuery site):
when code is hit, the some.php file is hit passing the name and location values in.
<script type="javascript">
function saveDataAjax(){
$.ajax({
type: "POST",
url: "some.php",
data: "name=John&location=Boston",
success: function(msg){
alert( "Data Saved: " + msg );
}
});
}
</script>
<input type="submit" onClick="saveDataAjax();" value="submit" />
It's a buzzword, the essence of it is:
Using Javascript to make an asynchronous HTTP request (in the background).
When the content arrives, an action is taken, usually performing some logic then updating the appearance of the page by manipulating the DOM tree; meaning, inserting new HTML elements, deleting some html elements, etc.
The X in AJAX stands for XML, but it's irrelevant. XML is just one of many ways to format the data that's sent by the server. JSON is a much better alternative (IMNSHO). Also, the server can send plain text or just regular html.
The keyword here is asynchronous request. A request that happens in the background, without the browser having to reload the page.
From the Pragmatic Ajax book:
What Is Ajax?
Ajax is a hard beast to distill into a
one-liner. The reason it is so hard is
because it has two sides to it:
Ajax can be viewed as a set of
technologies.
Ajax can be viewed
as an architecture.
Ajax: Asynchronous JavaScript and
XML
The name Ajax came from the bundling
of its enabling technologies: an
asynchronous communication channel
between the browser and server,
JavaScript, and XML. When it was
defined, it was envisioned as the
following:
Standards-based presentation using XHTML and CSS
Dynamic display and interaction using the browser’s DocumentObject
Model (DOM)
Data interchange and manipulation using XML and XSLT
Asynchronous data retrieval using XMLHttpRequest or XMLHTTP (from
Microsoft)
JavaScript binding everything together
Although it is common to develop using
these enabling technologies, it can
quickly become more trouble than
reward.
It is for these reasons that the more
important definition for Ajax is...
Ajax: The Architecture
The exciting evolution that is Ajax is
in how you architect web applications.
Let’s look first at the conventional
web architecture:
Define a page for every event in the application: view items, purchase
items, check out, and so on.
Each event, or action, returns a full page back to the browser.
That page is rendered to the user.
This seems natural to us now. It made
sense at the beginning of the Web, as
the Web wasn’t really about
applications. The Web started off as
more of a document repository; it was
a world in which you could simply link
between documents in an ad hoc way. It
was about document and data sharing,
not interactivity in any meaningful
sense.
Picture a rich desktop application for
a moment. Imagine what you would think
if, on every click, all of the
components on the application screen
redrew from scratch. Seems a little
nuts, doesn’t it? On the Web, that was
the world we inhabited until Ajax came
along.
Ajax is a new architecture. The
important parts of this architecture
are:
Small server-side events: Now components in a web application can
make small requests back to a server,
get some information, and tweak the
page that is viewed by changing the
DOM. No full page refresh.
Asynchronous: Requests posted back to the server don’t cause the
browser to block. The user can
continue to use other parts of the
application, and the UI can be updated
to alert the user that a request is
taking place.
onAnything: We can interact with the server based on almost anything
the user does. Modern browsers trap
most of the same user events as the
operating system: mouseovers, mouse
clicks, keypresses, etc. Any user
event can cause an asynchronous
request.
This all sounds great, doesn’t it?
With this change we have to be
careful, though. One of the greatest
things about the Web is that anybody
can use it. Having simple semantics
helps that happen. If we go overboard,
we might begin surprising the users
with new UI abstractions. This is a
common complaint with Flash UIs, where
users are confronted with new symbols,
metaphors, and required actions to
achieve useful results.
Most commonly, it refers to the use of the XMLHttpRequest object via JavaScript* in a browser.
Depending on who you ask, it could be used to describe almost any type of client/server communication over HTTP other than just typing a URL into a browser.
*jQuery provides some nice wrapper code to handle cross-browser differences, etc.
Ajax is a bit of a misnomer. To quote the wiki article:
Despite the name, the use of
JavaScript and XML is not actually
required, nor do the requests need to
be asynchronous.
Whereas now most people call "ajax" any type of
web application that communicates
with a server in the background
http://www.w3schools.com/Ajax/Default.Asp
that is a good place to start. This should answer all of your questions.
From the man that coined the term - http://adaptivepath.com/ideas/essays/archives/000385.php
"Ajax" is the successfull marketing term introduced back in 2005 to replace the the older term "DHTML" that did not stick well. "Ajax" today is part of the history too as the new word - "HTML5" emerge. Still "HTML5" is pretty much what original "DHTML" used to be.
Ajax is also reffered to as "the new approach to the application development" where a web page is created on the server initially but later on, during its lifetime, the updates are being done on the client as the data or partial content gets communicated to the server in a background.
Hope this clarifies.
Just to add.. may be not relevant for the question ..
although, AJAX was made famous by Gmail in their browser emails ..the credit of AJAX goes to Microsoft .. they created the AJAX thing..
I believe the fastest and easiest way to get started is with jQuery:
http://jquery.com/
http://docs.jquery.com/Ajax/jQuery.ajax#examples
AJAX stands for asynchronous JavaScript and XML, though it doesn't always deal with XML data anymore. Essentially it boils down to using the XMLHttpRequest object through JavaScript running on the client to make a web request and retrieve some information that you use to update the state of your page without requiring a page refresh.
Start with a basic tutorial that shows you how to use bare bones Ajax to make asynchronous requests such as http://www.w3schools.com/Ajax/Default.asp before moving on to using it in a production level application.
When using it in an application you're far better off investigating one of the common JavaScript frameworks that abstract away the differences between the various browsers and make it easy to manipulate the page after the request returns. I personally recommend http://www.jquery.com/
I read Head First AJAX as my first AJAX reference and I found it to give a simple and practical overview of AJAX.
Creative use of previously known technology. Both the browser side scripting and programmatic access to data on the server have been known before. In AJAX it has been put together for innovative use anabling new applications of thechology known before. The REST comes to mind as similar type of advance...
AJAX is very simple : someone somewhere tought that it would be cool to be able to send something to the server and receive something from it without reload a page.
AJAX is not a revolution, it's just a name for something simple : a web page can send a request to the server without being reloader - just some asynch stuff here.
You can add AJAX controls on your web pages wihout any works - just drag them in with Visual Studio. You may have to add some manager for them, but it is simply a drag-and-drop task.
But be warned : rogue web browser usually don't speak the same AJAX language as IE...
:)
AJAX is really fancy term for giving the browser the ability to refresh parts of its content with the need to reload an entire page. Like many have said, it doesn't require XML, or even Javascript in order to implement it. In fact in its early days it was done with with VBScript and Jscript and just called DHTML. Jesse James Garrett may have invented the AJAX term, but it was really Microsoft that invented the concept behind it.
This source says Microsoft started it in 1999, but I would date the birth of this technology even further. This Wired article is probably more accurate on the date of this technology being in the late 90's, much of it coming from the old days of the MSDN DHTML Dude columns written by Michael Wallent at Microsoft which started back in 1997. Much of the story is also told in this great video here by Michael himself: http://channel9.msdn.com/posts/Charles/Michael-Wallent-Advent-and-Evolution-of-WPF/ Megan still works at Microsoft by the way working on the Silverlight team nowadays, Microsoft's replacement for ActiveX.
Back to the AJAX thingy...when Jesse James Garrett back in 2005 he was mostly talking about the use of XMLHTTPRequest within Javascript code, and a dash of salt. That later began a hip word that many people started using even though they had no idea what it was, and thought that is really something brand new and hip, when really it was just a remix of something old.....sort of like many hip-hop songs you hear nowadays.
It's not new, just a newer version of something old!
I'll give it a try and say that "it's the concept of having a W3C based (JavaScript, HTML and CSS) solution for building Rich Applications for running on the web in a browser"
Everything else is just "technical details" I guess ... ;)
PS! - AMAZING question ...!! ;)
AJAX (Asynchronous JavaScript and XML) is a newly coined term for two powerful browser features that have been around for years, but were overlooked by many web developers until recently when applications such as Gmail, Google Suggest, and Google Maps hit the streets.
To know more information about Ajax learn Ajax tutorial
AJAX = Asynchronous JavaScript and XML.
AJAX is a technique for creating fast and dynamic web pages.
AJAX allows web pages to be updated asynchronously by exchanging small amounts of data with the server behind the scenes. This means that it is possible to update parts of a web page, without reloading the whole page.
Classic web pages, (which do not use AJAX) must reload the entire page if the content should change.
Examples of applications using AJAX: Google Maps, Gmail, Youtube, and Facebook tabs.(FROM w3school). to understand simply: when we request for a link or submit form we request a synchronously to server for data. webpage destroy current page and regenerate new page. but with AJAX browser can send the same request without repainting the entire page.
It's JavaScript, but it works.