WK4 - Quick glance at AJAX.

AJAX, acronym for Asynchronous JavaScript and XML, is a web development technique for creating interactive web application, its intent is to make web pages feel more responsive by exchanging small amount of data with sever behind the scenes. AJAX like DHTML, LAMP and SPA is not a technology in itself but a term of the use of a group of technologies.

AJAX uses a combination of, see figure 2.1:

1. XHTML and CSS, for markup and styling.


2. DOM accessed with client-side scripting language such as Javascript and JScript, for dynamically display and interact with the information presented.


3. XMLHttpRequest object, for exchanging data asynchronously with the web server.


4. XML, as a format for transferring data between server and client.

Pros and Cons

Pros:

1. an improvement to the user's experience;


2. cut down the bandwidth consumption, "load on demand";


3. encourage programmers to clearly separate the methods and formats used for the different aspects of information delivery via the web.

Cons:

1. transparent to the history, means that browser doesn't return desired result as triggering the "Back" button and make user difficult to bookmark a particular state of the page;


2. network latency may lead to the web page looks weird;


3. be careful the Javascript, because the different implementation by different browsers or versions of a particular browser.

Reference:

• AJAX in Action - Chapter 2;
• http://en.wikipedia.org/wiki/AJAX