// An example of using yield to simplify the callback hell.
// The limitation is, this only apply to whose callbacks take the normal form of function(err, result), more arguments are ignored.
// Maybe there are many workarounds, but keep it simple, the ECMAScript 6 is around the corner.

function Async(task) {
	
	var gen = task(callback);
	
	function callback(err, result) {
		
		if(err) {
			throw err;
		}
		else {
			gen.next(result);
		}
		
	};
	
	gen.next();
	
};

Async(function*(callback) {

	console.log(0);
	yield setTimeout(callback, 1000);
	console.log(1000);
	yield setTimeout(callback, 1000);
	console.log(2000);
	yield setTimeout(callback, 1000);
	console.log(3000);
	return;

});