observable-event-target
v0.2.1
Published
This is a sample implementation of `ObservableEventTarget` as [outlined in the Observable spec](https://github.com/tc39/proposal-observable).
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ObservableEventTarget
This is a sample implementation of ObservableEventTarget
as outlined in the Observable spec.
Step one is to make this example work:
const displayImage = document.querySelector("#displayImage");
const image = new Image();
const load = image.on('load', { receiveError: true, once: true });
image.src = "./possibleImage";
load.subscribe({
next(e) {
displayImage.src = e.target.src;
},
error(e) {
displayImage.src = "errorloading.png";
},
complete() {
// this notification will be received after next ()
// as a result of the once member being set to true
}
})
Interface as defined by the spec:
interface Event { /* https://dom.spec.whatwg.org/#event */ }
dictionary OnOptions {
// listen for an "error" event on the EventTarget,
// and send it to each Observer's error method
boolean receiveError = false;
// member indicates that the callback will not cancel
// the event by invoking preventDefault().
boolean passive = false;,
// handler function which can optionally execute stateful
// actions on the event before the event is dispatched to
// Observers (ex. event.preventDefault()).
EventHandler handler = null;
// member indicates that the Observable will complete after
// one event is dispatched.
boolean once = false;
}
interface ObservableEventTarget extends EventTarget {
Observable<Event> on(DOMString type, optional (OnOptions or boolean) options);
}
This implementation obviously draws heavily from the example implementation but was re-implemented from scratch as a learning exercise.