Click on the canvas to add more blobs. The colored buttons set the blob color. RND sets random color.

This works in Firefox, Safari, Chrome, and iPhone browsers, but renders verrry slowwwly in Internet Explorer.
This page uses HTML+Javascript without requiring any plugins such as Flash. To see how this is done, open this page and view source.

AJAX (Asynchronous Javascript and XML) is a technique for creating dynamic Web pages. AJAX is used to change elements of a Web page without reloading the whole page from the server, thus increasing performance and responsiveness. It was first named in 2005 and now is a relatively mature technology. All major browsers support it, popular sites use it heavily, and many Web development tools and languages build upon it. For more background about AJAX, see this Wikipedia article.

This page demonstrates basic AJAX functionality. The most popular way to use AJAX is via Javascript that is executed by user actions or a timer. The Javascript makes a request to the Web server, and when a response is received, HTML elements on the page are updated with the new information. Since this occurs asynchronously (in other words, is non-blocking), the user can interact with the Web page while AJAX request/response communication is happening, and so perceives that the page is more responsive.

Assume that you're building a Web page that displays a counter. This counter could show the number of messages the user has, time spent on the site, or similar information. You want the counter to get new information from the server without reloading the rest of the page.

Here are a counter and a button that uses AJAX to call a server-side method to update the counter's value:

Click on the button to see AJAX in action.

UTF_examples.zip contains the complete code examples for the book Unit Test Frameworks. It is free open source code. Most of the code requires a Java Development Kit (JDK) and JUnit. Some code uses GNU C++, Python and .NET. For a detailed explanation of the examples, read the book.