reconsider to add an async observation flavor

[gullerya]

Should it be possible to specify an async callbacks flavor?
If yes, shall I leverage an EventTarget object?

[gullerya]

I'm closing this again, I'll state few things to get to it back if needed in the future:

• it is not really any async unless got for some setTimeout stuff and probably even more relevant - requestAnimationFrame; but as soon as things become that complex - my feeling is that it should be kept consuming application concern; at the end of the day we are already running in some callback context, so it might quite be good enough to just run as fast as possible, synchronously and if any needed - use another streaming patterns to batch / async heavy processing
• no real use case so far seen for this scenario

[gullerya]

Reopening this to link to another issue, that actually will benefit from this one. So this is a use-case that justifies and async flavor.

[gullerya]

As it can be seen, the async behaviour, while not yet justified in itself, may serve the expected API behaviour like an Object.assign flow. In that use-case, while the native behaviour is to perform each and every property assignment on it's own, thus causing the changes delivery one per callback, the expected Observable API behaviour is to get the changes in batch. Async management of the changes delivery is enabler for that step.

[gullerya]

Design decision made thus far:

• async/sync changes delivery will be controllable on the level of Observable, nor lower than that (not per observer callback), nether higher - the whole framework
• the default flavour will remain the same - sync
• in order to make an Observable to dispatch the changes in async way the following API should be used (pay attention to the second options parameter):
  const oo = Observable.from({ <some object> }, { async: true });
• changes will be delayed later on in the same task, by queueMicrotask means
• if the callback causes new changes to be delivered, they'll be dispatched in the next microtask, not the currently running

[gullerya]

implemented in 3.2.0