An example of coroutines and a simple coroutine scheduler.

coroutineExperiment.js

function Dispatcher() {
	this.coroutine = null;
	this.loc = -1;
	this.stack = [];
}
Dispatcher.prototype.run = function* () {
	var returnValue = null;
	while (this.loc !== -1) {
		this.coroutine = stack[loc];
		const state = this.coroutine.next(returnValue !== null ? returnValue : undefined);
		returnValue = null;
		if (state.done) {
			this.stack.pop();
			this.loc--;
		} else if (state.type === "return") {
			returnValue = state.value;
			this.stack.pop();
			this.loc--;
		} else if (state.type === "call") {
			this.loc++;
			this.stack.push(state.functor);
		}
		yield;
	}
}
Dispatcher.prototype.runSync = function () {
	const runner = this.run();
	while (!runner.next().done);
};
Dispatcher.prototype.call = function(coroutune) {
	this.stack.push(coroutine);
}
function call(generator, args, thisArg) {
	return { type: "call", functor: generator.call(thisArg, args) };
}
function exit(value = null) {
	return { type: "yieldVal", value: value };
}
function generator1() {
	var loc = 0;
	const iterator = {
		done: false,
		next: function () {
			switch (loc) {
				case 0:
					console.log("Hello World");
					loc++;
					return iterator;
				case 1:
					console.log("Goodbye MoonMan");
					loc++;
					return iterator;
				case 2:
					console.log("What's up, doc?");
					iterator.done = true;
			}
			return iterator;
		}
	};
	return iterator;
}
function generator2(returnVal = null) {
	var loc = 0;
	const iterator = {
		done: false,
		next: function () {
			switch (loc) {
				case 0:
					loc++;
					return call(generator1);
				case 1:
					loc++;
					return exit("Test");
			}
			iterator.done = true;
			return iterator;
		}
	};
	return iterator;
}