async_concurrency_queue.js

function manager(tasks, worker, concurrency) {
    const res = [];

    function assign(w) {
        return new Promise((resolve) => {
            const t = tasks.shift();

            if (t === undefined) {
                return resolve();
            }

            console.log('assign %s', t);
            return w(t).then((r) => res.push(r))
                .then(() => assign(w))
                .then(resolve);
        });
    }

    return Promise.all(Array.from(new Array(concurrency)).map(() => assign(worker)))
        .then(() => res)
}

function worker(t) {
    return new Promise((r) => setTimeout(r, Math.random() * 1000))
        .then(() => `r_${t}`)
}


// Test
manager(
    [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10],
    worker,
    3
).then((r) => console.log(r));

My code is the same, but keep order of results, so it more close with bluebird.map