用 generator 实现 async/await

async_generator.js

const gFoo = function* () {
    const a = yield Promise.resolve(1)
    const b = yield Promise.resolve(2)
    const c = yield Promise.resolve(3)
    const d = yield Promise.resolve(4)

    return [a, b, c, d]
}

const co = genF => (...args) => {
    const gen = genF(...args)

    const h = toPass => {
        const { done, value } = gen.next(toPass)

        return done ?
            value :
            value.then(
                resolvedValue => h(resolvedValue)
            )
    }

    return h()
}

co(gFoo)().then(console.log)