AJAX-Driven Websites: Under The Hood
Asynchronous JavaScript, XML, and more!

ASP.Net 2.0
ASP.Net 2.0 significantly enhances the scripting model to incorporate this methodology. They call it script callbacks instead of Ajax. It works essentially the same as I described earlier, but ASP.Net 2.0 takes it a step further by providing tools and support. For a comprehensive explanation of script callbacks in ASP.Net 2.0, take a look at this article: http://msdn.microsoft.com/msdnmag/issues/04/08/CuttingEdge/.

Considerations
1.  Ajax blurs the line between correct tiering techniques since much of the work has been moved to the client. Consideration should be given when designing such applications using an emerging methodology. The client (browser) is doing more of the processing work, and the JavaScript to accomplish this is fairly complex. It's handling keystrokes, mouse clicks, interaction with the DOM, processing of these events, and data coordination with the server.

2.  It should also be noted that many users might not want to run JavaScript on their browsers. Your Web site audience is a consideration.

3.  The name Ajax is not official. The folks at Adaptive Path are given credit for this catchy name. In ASP.Net 2.0, it is referred to as "script callbacks."

References

About Tommy Newcomb
Tommy Newcomb works for Magenic as an IT consultant in the Chicago area.
His main focus is developing Web application and E-commerce work using Microsoft technologies. He lives with his wife, Emily, and baby daughter, Jaqueline, in the Chicago suburbs.

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Hi from Kartik

Recently, a number of Web sites have begun to raise some eyebrows within the developer community. What's unique about these sites is that they behave more like a desktop application than a Web application. As you interact with them, they quickly display an endless amount of information to your browser without reloading the page. At the Google Maps site for example (http://maps.google.com/), you can click on the map, zoom in, zoom out, and move around as much as you like. Your browser continues to be fed with data from the server, yet your browser doesn't have to refresh. They're not using applets, or anything like Flash, so how are they doing it? Introducing Asynchronous JavaScript + XML, also known as Ajax. To properly describe what Ajax is, it's easiest to contrast it with what it's not. For most Web sites, interaction with a Web server is simplex communication - like talking to your buddy on a walkie-talkie. You speak while he receives, and vice versa, but never at the same time. For a Web user, when he or she fills out an online form and then clicks the submit button, the entire page is posted to the Web server and the user must wait for the server to receive the request. When the server finishes processing the request, it sends the processed content back. Only then does the user's page finally refresh (see Figure 1). Ajax is an attempt to alleviate this choppy sequence of events. When the user is at an Ajax Web site the browser can call the Web server asynchronously, behind the scenes - without posting the entire page.

Recently, a number of Web sites have begun to raise some eyebrows within the developer community. What's unique about these sites is that they behave more like a desktop application than a Web application. As you interact with them, they quickly display an endless amount of information to your browser without reloading the page. At the Google Maps site for example (http://maps.google.com/), you can click on the map, zoom in, zoom out, and move around as much as you like. Your browser continues to be fed with data from the server, yet your browser doesn't have to refresh. They're not using applets, or anything like Flash, so how are they doing it? Introducing Asynchronous JavaScript + XML, also known as Ajax. To properly describe what Ajax is, it's easiest to contrast it with what it's not. For most Web sites, interaction with a Web server is simplex communication - like talking to your buddy on a walkie-talkie. You speak while he receives, and vice versa, but never at the same time. For a Web user, when he or she fills out an online form and then clicks the submit button, the entire page is posted to the Web server and the user must wait for the server to receive the request. When the server finishes processing the request, it sends the processed content back. Only then does the user's page finally refresh (see Figure 1). Ajax is an attempt to alleviate this choppy sequence of events. When the user is at an Ajax Web site the browser can call the Web server asynchronously, behind the scenes - without posting the entire page.

AJAX-Driven Websites: Under The Hood
Recently, a number of Web sites have begun to raise some eyebrows within the developer community. What's unique about these sites is that they behave more like a desktop application than a Web application. As you interact with them, they quickly display an endless amount of information to your browser without reloading the page. At the Google Maps site for example (http://maps.google.com/), you can click on the map, zoom in, zoom out, and move around as much as you like. Your browser continues to be fed with data from the server, yet your browser doesn't have to refresh. They're not using applets, or anything like Flash, so how are they doing it? Introducing Asynchronous JavaScript + XML, also known as Ajax. To properly describe what Ajax is, it's easiest to contrast it with what it's not. For most Web sites, interaction with a Web server is simplex communication - like talking to your buddy on a walkie-talkie. You speak while he receives, and vice versa, but never at the same time. For a Web user, when he or she fills out an online form and then clicks the submit button, the entire page is posted to the Web server and the user must wait for the server to receive the request. When the server finishes processing the request, it sends the processed content back. Only then does the user's page finally refresh (see Figure 1). Ajax is an attempt to alleviate this choppy sequence of events. When the user is at an Ajax Web site the browser can call the Web server asynchronously, behind the scenes - without posting the entire page.

AJAX-Driven Web Sites: Under The Hood. Recently, a number of Web sites have begun to raise some eyebrows within the developer community. What's unique about these sites is that they behave more like a desktop application than a Web application. As you interact with them, they quickly display an endless amount of information to your browser without reloading the page. At the Google Maps site for example (http://maps.google.com/), you can click on the map, zoom in, zoom out, and move around as much as you like. Your browser continues to be fed with data from the server, yet your browser doesn't have to refresh. They're not using applets, or anything like Flash, so how are they doing it? Introducing Asynchronous JavaScript + XML, also known as Ajax. To properly describe what Ajax is, it's easiest to contrast it with what it's not. For most Web sites, interaction with a Web server is simplex communication - like talking to your buddy on a walkie-talkie. You speak while he receives, and vice versa, but never at the same time. For a Web user, when he or she fills out an online form and then clicks the submit button, the entire page is posted to the Web server and the user must wait for the server to receive the request. When the server finishes processing the request, it sends the processed content back. Only then does the user's page finally refresh (see Figure 1). Ajax is an attempt to alleviate this choppy sequence of events. When the user is at an Ajax Web site the browser can call the Web server asynchronously, behind the scenes - without posting the entire page.

Recently, a number of Web sites have begun to raise some eyebrows within the developer community. What's unique about these sites is that they behave more like a desktop application than a Web application. As you interact with them, they quickly display an endless amount of information to your browser without reloading the page. At the Google Maps site for example (http://maps.google.com/), you can click on the map, zoom in, zoom out, and move around as much as you like. Your browser continues to be fed with data from the server, yet your browser doesn't have to refresh. They're not using applets, or anything like Flash, so how are they doing it?

Recently, a number of Web sites have begun to raise some eyebrows within the developer community. What's unique about these sites is that they behave more like a desktop application than a Web application. As you interact with them, they quickly display an endless amount of information to your browser without reloading the page. At the Google Maps site for example (http://maps.google.com/), you can click on the map, zoom in, zoom out, and move around as much as you like. Your browser continues to be fed with data from the server, yet your browser doesn't have to refresh. They're not using applets, or anything like Flash, so how are they doing it? Introducing Asynchronous JavaScript + XML, also known as Ajax. To properly describe what Ajax is, it's easiest to contrast it with what it's not. For most Web sites, interaction with a Web server is simplex communication - like talking to your buddy on a walkie-talkie. You speak while he receives, and vice versa, but never at the same time. For a Web user, when he or she fills out an online form and then clicks the submit button, the entire page is posted to the Web server and the user must wait for the server to receive the request. When the server finishes processing the request, it sends the processed content back. Only then does the user's page finally refresh (see Figure 1). Ajax is an attempt to alleviate this choppy sequence of events. When the user is at an Ajax Web site the browser can call the Web server asynchronously, behind the scenes - without posting the entire page.


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