Illustrating asynquence "Iterable Sequences"

ex1-sync-iteration.js

function step(num) {
	return num * 2;
}

// set up an iterable sequence
var isq = ASQ.iterable()
	.then(step)
	.then(step)
	.then(step);

// synchronously iterate the sequence
for (var seed = 3, ret;
	// call `next(..)` on the iterable sequence
	// to advance it one iteration
	(ret = isq.next(seed)) && !ret.done;
) {
	seed = ret.value;
	console.log(seed);
}
// 6
// 12
// 24

ex2-async-iteration.js

function step(num) {
	return num * 2;
}

function iterate(msg) {
	// call `next(..)` on the iterable sequence
	// to advance it one iteration
	var ret = isq.next(msg);
	if (!ret.done) {
		return ret.value;
	}
	else {
		// break the iteration loop
		throw "Iteration complete.";
	}
}

// set up an iterable sequence
var isq = ASQ.iterable()
	.then(step)
	.then(step)
	.then(step)
	.then(function(){
		throw "Should not get here!";
	})
	.or(function(msg){
		console.log(msg); // Too big!
	});

// set up an async loop sequence controller
loop = ASQ()
.or(function(msg){
	console.log(msg); // Iteration complete.
	console.log(seed); // 24
});

// asynchronously iterate the sequence
(function next(msg){
	if (msg > 15) {
		// throw an error into the iterable
		// sequence
		sq.throw("Too big!");
	}

	// store seed so we can check it at the end
	seed = msg;

	loop
	// wait before proceeding with the iteration
	.then(function(done){
		setTimeout(done,50);
	})
	.val(
		// inject `msg` into the sequence's
		// message stream
		msg,
		// process the current iteration
		iterate,
		// start up the next loop iteration
		next
	);
})(3); // start out msg/step as `3`