asyncPool.js

asyncPool

async function asyncPool(poolSize, inputArray, fn) {
  const all = [];
  const inProgress = [];
  for (const data of inputArray) {
    const p = new Promise(resolve => resolve(fn(data)));
    all.push(p);
    if (inputArray.length > poolSize) {
      const e = p.then(() =>  inProgress.splice(inProgress.indexOf(p), 1));
      inProgress.push(e);
      if (inProgress.length >= poolSize) {
        console.log('wait until at least one is done and the pool is available')
        await Promise.race(inProgress);
      }
    }
  }
  return Promise.all(all);
}

asyncPool(2, [1, 2, 3], (i) => i * 2).then(r => console.log(r))