Processing an array of promises* in batches of X requests at a time

batch.js

/**
 * (*) Due to the eager nature of promises, `items` must be an
 * array of promise returning functions and not an array of promises
 */
const batchProcess = (count, items) => {
  const chunked = R.splitEvery(count, items);
  
  const process = async ([head, ...tail]) => {
    const promises = head.map(func => func());
     const results = await Promise.all(promises);
    
    if (!tail.length) {
      return results;
    }
    
    return [...results, ...await process(tail)];
  }
  
  return process(chunked);
}

const results = await batchProcess(50, aVeryVeryLargeAmountOfRequests);