I have a $w.Button "myBtn" for example to "create a new record". I want to hook up a function to its click event. However my function is inside a class object e.g. myObj.new_click() and the function needs access to the object's members/functions such as name of dataset etc.
However because it does not have context of the myObj, the code inside the myObj.on_click() would not be able to access myObj's member functions etc.
So if I could hook up myObj with myBtn as some kind of app specific data (e.g. appData) ... the event handler could get it back from event.target.appData and then it can access myObj members.