The Greet.create() calls that follow add three instances of the new Greet class to the demo. However, since Greet currently has no meaningful pre-defined content, the three controls don’t appear to be visible.
Your goal: Add default content to Greet controls by giving the “content:” key a string value like “Hello, world!”
When Greet.create() is called, a plain instance of the base Control class is created. The string you specify will then be passed to the Control class’ content() property, which will insert the text into the control’s top element. When the resulting elements are passed to $demo.append(), you end up seeing three copies of the text.