Even though Dojo is made up of many different packages, it's frequently used in very specific ways. Because of this, we've created special editions of Dojo aimed toward these users. A visit to dojo's download page will show you which editions are currently available, such as the Ajax and Widget edition.

An edition is very simple, really. The important file is dojo.js, which is created by merging the most frequently used packages and compressing the resulting code. This means that when you have a script tag that calls dojo.js, you're getting not just the basic Dojo codebase, but the additional functionality that is most pertinent to your specific use.

You might wonder why so much additional code comes in each edition. This is the full code base, and allows you to use functionality that is outside of your specific build. It means that even if you have a very specifically tailored edition of Dojo, you aren't limited to only using that featureset. If your site uses the event and I/O systems heavily, but one of your pages uses a widget, then you don't have to worry that your widget will break. This also means that any of the examples in this book will work no matter what edition you've downloaded.