runGenerator.js

function isPromise(thing) {

    return (
        typeof thing === "object" && thing !== null
        && thing.then instanceof Function
        && thing.catch instanceof Function
    );
}

function whileGenerates(gen, prevGenResult) {

	if (isPromise(prevGenResult.value)) {
		prevGenResult.value
			.then(promResult => whileGenerates(gen, gen.next(promResult)))
			.catch(gen.throw.bind(gen));
	}
	else if (prevGenResult.value instanceof Error) {
		gen.throw(prevGenResult.value);
	}
	else if (!prevGenResult.done) {
		whileGenerates(gen, gen.next(prevGenResult.value));
	}
}

function runGenerator(generator) {
    "use strict";

    let gen = generator();
    whileGenerates(gen, gen.next());
}

// TEST

function asyncTask(timeoutMs, error, result) {

    return new Promise(
        (resolve, reject) => setTimeout(
            () => error
                ? reject(error)
                : resolve(result),
            timeoutMs
        )
    );
}

runGenerator(function* () {
    "use strict";

    console.time("async1");
    let result = yield asyncTask(3000, null, "async task #1 result");
    console.timeEnd("async1");
    console.log(result);
    
    try {
        console.time("async2");
        result = yield asyncTask(5000, new Error("async task #1 error"));
    }
    catch (error) {
        console.timeEnd("async2");
        console.error(error);
    }
});