What I don't understand is why onload and onerror need a return value? I
just return null as I've no clue what the return value should be.
Because these on<Event> properties and their functions are defined that
way. For example in the old days you could return false in an onclick
function to suppress the click default action of the browser. These days it
is recommended to always use addEventListener() instead of these event
properties and to suppress the default action you call
event.preventDefault().
Also in JS a function basically always have some return value, e.g.
function() {
return;
return undefined;
// no return statement at all
}
is all the same and returns undefined. That is why Promises in elemental2
also feel a bit clunky compared to JS. Promises allow you to return a new
Promise/thenable in your success/catch callback methods so elemental2 has
to define a return type for these callback functions. If you do not want to
return a Promise/thenable in JS then you simply do not write a return
statement but in Java you now have to write return null.
-- J.
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