IntelliJ idea is the same as the Java IDE, and Eclipse, because of the gorgeous interface and innovative features of many Java programmers love (unfortunately not free).
Adapting to Ajax development trends, Idea 5.1 provides support for JavaScript, with current features:
Code Reminders
Variable refactoring
Create a new method assistant
The Web site also provides a flash demo on how to use the new features for Ajax development, and you can see from the preview that the AJAX framework used in the demo is Prototype.
To build a perfect AJAX development environment, idea is not going far enough, but it's always a start. IntelliJ Idea 6.0 EAP version has also been released, code-named Demetra, is said to be a new version of Web development will provide more extensive support.
Of course, the most anticipated is the OpenAjax plan under the armed eclipse early debut.