How does AJAX work?
JavascriptAjaxJavascript Problem Overview
What is the essence of AJAX? For example, I want to have a link on my page such that when a user clicks this link, some information is sent to my server without the reloading of the current page. Is that AJAX?
I was able to get this behavior by using isoframes. In more details I put a link (let's say a small image) in a small isoframe. When the user clicks this link the browser reloads only the page in the isoframe.
However, I think it is not an elegant way to reach the goal. I think I have to use AJAX. How does it work? Can a usage of XHTML solve the considered problem in an elegant way? Or do I need to use JavaScripts?
I do not need much. I just want to have a small link which (after clicking) sent some information to server. Let say I have a "star-image" near a message. If a user click the star (he/she likes the message) star changes the color and my server update database (to remember that user likes the message).
Javascript Solutions
Solution 1 - Javascript
If you are totally new to AJAX (which stands for Asynchronous Javascript And XML), the AJAX entry on wikipedia is a good starting point:
> Like DHTML and LAMP, AJAX is not a technology in itself, but a group of technologies. AJAX uses a combination of:
>
> * HTML and CSS for marking up and
> styling information.
> * The DOM
> accessed with JavaScript to
> dynamically display and interact with
> the information presented.
> * A method
> for exchanging data asynchronously
> between browser and server, thereby
> avoiding page reloads. The
> XMLHttpRequest (XHR) object is usually
> used, but sometimes an IFrame object
> or a dynamically added
Solution 2 - Javascript
AJAX typically involves sending HTTP requests from client to server and processing the server's response, without reloading the entire page. (Asynchronously).
Javascript generally does the submission and receives the data response from the server (traditionally XML, often other less verbose formats like JSON)
The Javascript then may update the page DOM dynamically to update the user's view.
Thus 'Asychronous Javascript And XML'.
There are other options to update the user's view without reloading the page, things like Flash and Applets, but these don't sound like good solutions for your case. Sounds like Javascript is the way to go. There's loads of good library support around, like jQuery as is used on this site, so you don't need to actually write much Javascript yourself.
Solution 3 - Javascript
The essence of AJAX is this:
Your pages can browse the web and update their own content while the user is doing other things.
That is, your javascript can send asynchronous GET and POST requests (usually via an XMLHttpRequest object) then use the results of those requests to modify its page (via Document Object Model manipulation).
Solution 4 - Javascript
Ajax is more than reload just a part of the page. Ajax stands for Asynchronous Javascript And Xml.
The only part of Ajax that you need is the XMLHttpRequest object from javascript. You have to use it to load and reload small part of your html as a div or any other tags.
Read that example and you will be pro sooner as you think!
<html>
<body>
<script type="text/javascript">
function ajaxFunction()
{
var xmlhttp;
if (window.XMLHttpRequest)
{
// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp=new XMLHttpRequest();
}
else if (window.ActiveXObject)
{
// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
else
{
alert("Your browser does not support XMLHTTP!");
}
xmlhttp.onreadystatechange=function()
{
if(xmlhttp.readyState==4)
{
document.myForm.time.value=xmlhttp.responseText;
}
}
xmlhttp.open("GET","time.asp",true);
xmlhttp.send(null);
}
</script>
<form name="myForm">
Name: <input type="text" name="username" onkeyup="ajaxFunction();" />
Time: <input type="text" name="time" />
</form>
</body>
</html>
Solution 5 - Javascript
AJAX stands for Asynchronous Javascript and XML. AJAX supports partial updates to pages without having to post the entire page back to the server.
There are plenty of options for AJAX. The two most notable (arguably) are Microsoft's ASP.NET AJAX (formerly Atlas) and jQuery.
ASP.NET AJAX is relatively easy to set up if you're already familiar with ASP.NET. jQuery is good if you already know javascript, and allows very granular control over the querying and updating of your page.
HTH
Solution 6 - Javascript
If you're interested, IBM have a 10 (possibly more) part series on Ajax: Mastering Ajax part 1
Although a few years old now it's a good intro, (even if you just read the first part!)
I think the whole series should be listed Here, although the site's being a bit slow for me at the moment...
Summary: > Ajax, which consists of HTML, JavaScript™ technology, DHTML, and DOM, is an outstanding approach that helps you transform clunky Web interfaces into interactive Ajax applications. The author, an Ajax expert, demonstrates how these technologies work together -- from an overview to a detailed look -- to make extremely efficient Web development an easy reality. He also unveils the central concepts of Ajax, including the XMLHttpRequest object.
Solution 7 - Javascript
that is ajax. you cannot use ajax without javascript. you should look at jquery and prototype examples to get an idea of usage.
Solution 8 - Javascript
What you are trying to do is technically ajax. Ajax creates xhtml fragment transactions to update sections of a page. Javascript makes these get requests nice and neat.