Prior to Dojo 0.9 it was apparently possible to add a custom HTML attribute to a widget and then retrieve that custom attribute from the JavaScript extraArgs array. This functionality was dropped as evidenced by:

http://dojotoolkit.org/book/dojo-porting-guide-0-4-x-0-9/widgets/custom

where it states:

extraArgs - deleted - declare all parameters to your widget as attributes in the widget

Say that I would like to add the following custom attribute myAttribute as follows: