Work Queue

work-queue.mjs

import { promisify } from 'util';
const sleep = promisify(setTimeout);

class WorkQueue {
    #gen;

    constructor() {
        const gen = WorkQueue.#processor();
        gen.next(); // ignore first call
        this.#gen = gen;
    }
    static async *#processor() {
        let result;
        while (true) {
            const [process, payload] = yield result;
            result = await process(payload);
        }
    }
    async enqueue(payload, callback) {
        const result = await this.#gen.next([callback, payload]);
        return result.value;
    }
}

const wq = new WorkQueue();

async function processJob1() {
    console.log('3');
    console.log(await wq.enqueue(3, async (payload) => {
        await sleep(1000);
        return payload ** 2;
    }));
}

async function processJob2() {
    console.log('2');
    console.log(await wq.enqueue(2, async (payload) => {
        await sleep(500);
        return payload ** 4;
    }));
}

async function processJob3() {
    console.log('throw error');
    try {
        await wq.enqueue(undefined, () => {
            throw new Error('err');
        });
    } catch (ex) {
        console.log(ex.message);
    }
}

processJob1();
processJob2();
processJob3();