Dijit is a fantastic layer of widgets that provides a complete collection of out-of-the-box form elements, layout containers, and other common controls for achieving a rich user experience on the web. Dijit builds directly on the foundation provided by Base and Core, and is a prime example of the kind of achievement that is possible from using a powerful standard library that insulates you from browser inconsistencies and reduces the boilerplate that you normally write, debug, test, and maintain along the way. In that regard, Dijit is very much the natural outworking of Base and Core.
Of course, there is tremendous power in having the ability to write your own custom dijits—whether totally from scratch or as a composition of existing stock dijits—so there will be plenty of coverage on that front as well. Digging deep into the anatomy and lifecycle of widgets, mapping out the parallels between declaring widgets in markup versus programmatic creation, and discussing accessibility (a11y, which is an abbreviation for “accessibility” in that the word starts with “a,” ends with “y,” and has 11 letters in between) are all on the agenda.