AsyncM

Declarative asynchronous control flow

This library provides a way to manage async control flow and be able to cancel some computations, if needed.

Callback hell is solved by Promises, which are, in fact, only subscription for some result, but not controllers of computations.

AsyncM objects, therefore, defining some computations, that can be runned and will return controller of this runned computation.

AsyncM objects have next methods:

• .run(onResult, onError, onCancel) → {cancel: Function<Object, AsyncM>} — starts computation, returns object, that have method to cancel it
• .next(resultHandler, errorHandler, cancelHandler) → AsyncM — immutable operation

Also, there is shortcuts:

• .result(resultHandler), .error(errorHandler), .cancel(cancelHandler)
• .skipResult(asyncM), .skipError(asyncM), .skipAny(asyncM)

Handlers that are passed in run method are just callbacks, handlers that passed in next can return new AsyncM object that will continue computation as in Promises.

If cancel method of run result object is called and runned, all result/error handlers are ignored and then cancelHandlers are called for each layer of handlers. It is easiest to demonstate, than to describe:

var running = AsyncM.sleep(10).result(function() {
	return AsyncM.sleep(100).cancel(function() {
		console.log(1);
	}).result(function() {
		return AsyncM.sleep(500).result(function() {
			console.log(2);
		}).cancel(function() {
			console.log(3);
		});
	}).cancel(function() {
		console.log(4);
	}).cancel(function() {
		console.log(5);
	})
}).cancel(function() {
	console.log(6);
}).run();

setTimeout(function() {
	running.cancel().run();
}, 200)

In result of execution that code will print only 3, 4 and 6.

• 1 will be not printed cause 10ms + 110ms passed and this operations are already got executed
• 2 will be not printed cause it need to await 10ms + 110ms + 500ms, but operation is cancelled at 200ms and handler will be not called (and setTimeout for this 500ms is cleared)
• 5 will be not printed cause at this layer one cancelHandler, that follows execution order already executed

... to be continued