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Posted 28 Jan 2013

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What is AJAX?

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28 Jan 2013CPOL5 min read
What is AJAX?
What is AJAX?

People are always looking for ways to make their websites dynamic and interactive. Most of the time, they ‘usually’ ask Google, find this, find that, etc… and when they find what they are looking for, all they do is Copy/Paste, test, and if it works, then boom!  They are done. If it doesn’t work, then the cycle repeats, until it does. At least, that’s what I used to do in past. This tends to happen very often when creating interactive websites using jQuery and AJAX. So honestly, how many of you know exactly what AJAX is? Today I feel like writing a little more about what AJAX is and how it works.


AJAX is just an acronym refering to Asynchronous JAvaScript and XML. Now, if we take a look those words, most of us know what JavaScript and XML are, but the term Asynchronous can be confusing, so let’s focus on that.

What does asynchronous refer to?

Asynchronous refers to events that are happening on the background independently of the main application flow. These events do not disturb the flow of the application, allowing the continuation of it’s normal process. A fairly good example of this happening is in your Facebook home page, when all of a sudden, without refreshing your browser window, you notice that there are new status feed updates from your friends. ( Although I did notice, and think many have as well, how they do implement this. If you haven’t then, try leaving your facebook homepage on the browser without moving your mouse for about 1 minute. After that minute, just move your mouse from one point to another, and all of a sudden, you will see the feeds get updated. ) I’m assuming they are using some jQuery mousemove or something similar for this to happen. So what happens there is, facebook sends your profile information ( or your user id ) to their servers. Their servers then look for your friends list, grab their newly added status, return the result to the browser and then add them to your wall so that you can see. All of that, without pressing that refresh button.

So you see, AJAX allos you to update a web page asynchronously on the background by exchanging simple, and small amounts of data. Some more examples of pages using AJAX is: Youtube, Gmail, Google Maps, StackOverflow and many more on the web.

So you are still asking yourself, What is AJAX? Well, I’m going to ask for forgiveness, as I have no art skills, but the following image should help you just a little bit.

AJAX Cycle

Some advantages

AJAX, you see, is based on internet standards. It uses a combination of the following to accomplish it’s goal:

  • XMLHttpRequest Object(Modern Broswers and IE7+)
  • ActiveXObject (IE6 and below)
  • JavaScript/DOM (Used to interact browser and server)
  • XML (Returned results)
  • JSON (Returned results)
  • HTML (Returned results)

These standards are browser based, making them platform independent. It doesn’t matter where you program this in, as long as you have a browser, then this ‘should’ work. All you would need is a server with the application files, and the browser should do the rest. 

Another advantage using AJAX would be a better user interactivity. This could be named the most obvious benefit of using AJAX, and why web developers and webmasters are using AJAX more and more every day. AJAX simplifies the flow of an application, thus making it have quicker interaction between user and website since pages are not reloaded for content to be displayed. This activity can be simplified, since the loading times can be reduced from websites.

The advantage above opens up for this next advantage, which you can call it, smoother navigation on a website. While using AJAX, users will not have the need to use the refresh nor the back button, thus, allowing quicker response from the server.

Some Disadvantages

Everything that has an advantage, will most likely have disadvantages, and AJAX surely has some that I will mention.

Even though the back and refresh button are not needed while navigating a website with AJAX, these two buttons can become useless. This is due to the fact that, AJAX ‘navigating’ does not change you URL, so if you were in the middle of a process, and have no direct URL to where you were, then this might be bad. In some cases, the use of Hijaxing is used, which is the use of hashing url (#) at the end.

Another disadvantage would be that it is dependant on JavaScript. While it is ok to depend on it, since most modern (if not all) already use it, but in some cases, there are users who prefer disabling JavaScript. This makes AJAX worthless. Gladly, there is a workaround this problem, as web developers must have in mind, every time they create an AJAX Website, they need to always think of this and make an optional non-AJAX version of the AJAXified website they just created. 

The last disadvantage I want to point out would be the SEO factor. Since there are no SEO Friendly URL’s, then search engine tend to bypass your application, and it would appear as if that part of your site does not exist.

My recommendations

Before coding your AJAX website, make sure you think of the listed disadvantages and obviously many more. Remeber, when creating a website, you have to think on customer/client satisfaction, not your own. You have to always think of all, and I mean ALL common browsers, including IE6.

The post What is AJAX? appeared first on Jotorres Web Development.

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This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Software Developer
Puerto Rico Puerto Rico
As a computer scientist, I strive to learn more everyday in my field. Everything I learn, I share with my community by writing articles for future references.

Comments and Discussions

GeneralVery Useful Thanks. Pin
Mahmoud_Mohamed14-Jun-14 6:48
MemberMahmoud_Mohamed14-Jun-14 6:48 
GeneralMy vote of 5 Pin
Mehdi Haghgoo17-Jun-13 22:21
MemberMehdi Haghgoo17-Jun-13 22:21 
GeneralThanks Pin
Meshalawy19-Apr-13 6:42
MemberMeshalawy19-Apr-13 6:42 
GeneralMy vote of 1 Pin
yannman31-Jan-13 12:43
Memberyannman31-Jan-13 12:43 
QuestionThis article is so 2005... Thank you for this leap in the past! Pin
yannman31-Jan-13 12:39
Memberyannman31-Jan-13 12:39 
GeneralMy vote of 4 Pin
Shubh Agrahari29-Jan-13 4:00
MemberShubh Agrahari29-Jan-13 4:00 
GeneralRe: My vote of 4 Pin
jotorres29-Jan-13 4:54
Memberjotorres29-Jan-13 4:54 

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