JobQueue using pure async/await

JobQueue.js

// A job queue that takes an anonymous functions and executes them in parallel
let maxConcurrent = 3;
let queue = [];
let activeCount = 0;

// Add task to queue and execute
async function exec(task) {
  queue.push(task);
  await next();
}

// Process the next task in the queue
async function next() {
  if (activeCount < maxConcurrent && queue.length > 0) {
    const nextTask = queue.shift();
    activeCount++;

    try {
      // Await the task's execution and propagate the result (resolve or reject)
      await nextTask();
    } catch (error) {
      // Handle errors or add retry logic here
      console.error("Task failed:", error);
    } finally {
      activeCount--;
      next(); // Process the next task once this one is finished
    }
  }
}

const setMaxConcurrent = (n) => {
  maxConcurrent = n;
};

module.export = { exec, setMaxConcurrent };

// Usage

const sleep = (ms) => new Promise((r) => setTimeout(r, ms));

const Job = async (id, delay) => {
  console.log(`Task ${id} added`);
  await sleep(delay);
  if (id === 2) {
    throw new Error("err happened");
  }
  console.log(`Task ${id} done`);
};

exec(() => Job(1, 1000));
exec(() => Job(2, 750));
exec(() => Job(3, 2000));
exec(() => Job(4, 2500));
exec(() => Job(5, 1000));
exec(() => Job(6, 250));