Dojo: The Definitive Guide

Chapter 12. Dijit Anatomy and Lifecycle

Like object-oriented concepts from any other programming paradigm, Dojo widgets—dijits—follow particular patterns for lifecycle events such as creation and destruction, are composed according to a particular an anatomical style, and are described by a somewhat specialized vocabulary. This chapter provides a summary of these topics with an extended discussion on the fundamentals of custom dijit design.

Dijit Anatomy

Although you already know that dijit is short for "Dojo widget," it's helpful to elaborate just a bit before we proceed any further. To be precise, a dijit is any Dojo class that inherits from a foundational class from Dijit called _Widget. This class is part of the toolkit's foundational dijit module, so the fully qualified name of the class is dijit._Widget. There are several other foundational classes from Dijit that you'll learn about, but _Widget is the one that provides the primary ancestor for any dijit.

As you learned in Chapter 10, dojo.declare saves you from writing a lot of mundane boilerplate; dijits follow suit by tucking away a lot of complexity in classes like _Widget. As you're about to see, there are a number of method stubs that you can override to achieve custom behavior, as opposed to engineering your own boilerplate.

Tip

You may be wondering why the _Widget class is prefixed with a leading underscore. When used in relation to dijits, the leading underscore almost always means that it should not be instantiated on ...