Example 6-24. Sample async wrapper

function async(generator) {
	return function () {
		var iterator = generator.apply(this, arguments);

		function handle(result) {
			if (result.done) return Promise.resolve(result.value);
			return Promise.resolve(result.value).then(function (res) {
				return handle(iterator.next(res));
			}, function (err) {
				return handle(iterator.throw(err));
			});
		}

		try {
			return handle(iterator.next());
		} catch (ex) {
			return Promise.reject(ex);
		}
	};
}