I'm not entirely clear on what exactly you're trying to achieve. Could you provide some more background and details?
Are you trying to put the name of a widget in the class of the widget? Or the ID? If it's a Mendix Widget/UI element (I think this is what you mean), there will be a classname indicating what it is in the top HTML element, with a mx- prefix.
Example at https://ux.mendix.com/theme-creator.html:
<div class="mx-navigationtree mx-name-navigationTree2" id="mxui_widget_NavigationTree_1" widgetid="mxui_widget_NavigationTree_1">
mx-navigationtree indicates that it's a navigation tree, as will mx-datagrid be added as a class for a datagrid, etc. You can use these classnames, combined with IDs for automated testing.
Does this answer your question?
This will actually contain all the names of the widgets as keys in this object