The whole solution of Ajax technology Two

The term Ajax is used to describe a set of techniques that enable browsers to provide a more natural browsing experience for users. Before Ajax, the Web site forced the user into the Submit/wait/display paradigm, and the user's actions were always synchronized with the server's "Think Time." Ajax provides the ability to communicate asynchronously with the server, freeing users from the request/response loop. With Ajax, you can use JavaScript and DHTML to update the UI immediately when the user clicks the button, and to send an asynchronous request to the server to perform an update or query the database. When the request returns, you can use JavaScript and CSS to update the UI appropriately instead of refreshing the entire page. Most importantly, the user doesn't even know that the browser is communicating with the server: The Web site appears to be responding instantly.

While the infrastructure required for Ajax has been on for some time, the true power of the recent asynchronous request has not been exploited. Being able to have a very responsive web site is really exciting because it ultimately allows developers and designers to create "desktop-style (desktop-like)" Usability using standard html/css/javascript stacks.

Comparison with traditional Web applications

Traditional Web applications allow users to fill out forms, sending a request to the Web server when a form is submitted. The server receives and processes the form, and then returns a new page. This approach wastes a lot of bandwidth because most of the HTML code in the front and back two pages is often the same. Because each application interaction needs to send a request to the server, the response time of the application depends on the response time of the server. This causes the user interface to respond much more slowly than the local application.

In contrast, AJAX applications can send and retrieve only the necessary data to the server, using SOAP or some other xml-based Web service interface, and using JavaScript on the client to handle the response from the server. Because the amount of data exchanged between the server and the browser is much reduced, the result is that we can see applications that respond faster. At the same time, a lot of processing work can be done on the requesting client machine, so the Web server has less processing time.

How Ajax Works

The core of Ajax is the JavaScript object XMLHttpRequest. This object was first introduced in Internet Explorer 5, which is a technology that supports asynchronous requests. In short, XMLHttpRequest allows you to use JavaScript to make requests to the server and process the response without blocking the user.

When you create a Web site, performing a screen update on the client provides a lot of flexibility for the user. Here are the features you can do with Ajax:

Dynamically update the total number of items in a shopping cart without requiring the user to click Update and wait for the server to resend the entire page.

Improves the performance of the site by reducing the amount of data downloaded from the server. For example, on Amazon's shopping cart page, when the number of items in the basket is updated, the entire page is loaded, which must download 32K of data. If you use Ajax to calculate the new total, the server will only return the new total, so the required bandwidth is only 1%.

Eliminates page refreshes each time the user enters. For example, in Ajax, if a user clicks Next on a paging list, the server data refreshes the list instead of the entire page.

Edit the table data directly instead of requiring the user to navigate to the new page to edit the data. For Ajax, when a user clicks Edit, the static table can be refreshed to a table that is editable by the content. After the user clicks Done, an AJAX request can be made to update the server and refresh the table so that it contains static, read-only data.