trampoline.js

function Trampoline(func) {
	this.task = new Task(func);
}

Trampoline.prototype.step = function() {
	if (!this.task) return;
	this.task = this.task.cont();
	if (this.task) this.task.nextStep = this.step.bind(this);
};

Trampoline.prototype.cancel = function() {
	if (this.task && this.task.canceler) {
		this.task.canceler();
	}
	this.task = null;
}

function Task(cont) {
	this.cont = cont;
	this.nextStep = null;
	this.canceler = null;
}

Task.prototype.getCallback = function() {
	var self = this;
	return function() { self.nextStep() };
};

function wait(cont, sec) {
	var task = new Task(cont);
	var timerId = setTimeout(task.getCallback(), sec * 1000);
	task.canceler = function() { clearTimeout(timerId) };
	return task;
}

function f1() {
	console.log(1);
	return wait(f2, 1);
}

function f2() {
	console.log(2);
	return wait(f3, 1);
}

function f3() {
	console.log(3);
	return null;
}

var trampoline = new Trampoline(f1);
trampoline.step();
setTimeout(function () {
	console.log("cancel!");
	trampoline.cancel();
}, 1500);