example[spec] Add a listener to a widget

" self is a coordinator "
| jsObject js widgets tasks listeners newHandler tasksSpec tasksWidget |
newHandler := [ Transcript show: 'OK!'].
jsObject := self template basicAt: #spec. 
js := JS @ jsObject. 
widgets := (JS @ (js @ #configuration)) @ #widgets.
tasksSpec := (JS @ widgets) @ #tasks.
listeners := (JS @ ((JS @ tasksSpec) @ #configuration)) @ #listeners.

" install a new listener on #tasks widget "
(JS @ listeners) handleAt: #testingEvent put: newHandler.

" self is a coordinator "
tasksWidget := self widgetAt: #tasks. 

" trigger event "
tasksWidget triggerEvent: #testingEvent