Warnings:

• There have always been undocumented features in the web browsers. Some of these were uncovered during the preparation of this book and have been covered in their own topics.

• Generally, the undocumented features are methods and properties of objects that are not commonly used and maybe an extension to the object that is platform specific. There are also objects that are obscure, and can only be discovered by inspection.

• Reading the standards documents, release notes, and manufacturer manuals, only reveals part of the picture.

• The most powerful tool for uncovering these undocumented features is JavaScript itself. In particular the for( ... in ... ) enumerator which will scan an object for any enumerable properties. This won't reveal all the hidden features but it will uncover many of them.

• Armed with this knowledge, you can write inspection scripts to display the values of those properties. Often they point at an object and if the property is undocumented, then it's likely the object is as well.

• You can spend many hours examining a new browser release and learn much about how it's organized internally. This helps to better understand DOM navigation and how to do 'extreme JavaScript programming'.

• MSIE version 5.0 and 5.5 both introduce many interesting and undocumented features. Netscape version 6.0 builds on that, and adds many more, in particular the sidebar. A great deal of Netscape's user interface is written in JavaScript and by examining the Mozilla source code and the .js files that are installed with it, you can learn and possibly customize your browsing experience.