runBounded.ts

runBounded.ts

export async function runBounded<T>(
  tasks: Array<() => Promise<T>>,
  concurrency: number
): Promise<T[]> {
  const results: T[] = new Array(tasks.length);

  let nextIndex = 0;
  let failed = false;

  async function runner() {
    while (!failed) {
      const index = nextIndex++;

      if (index >= tasks.length) {
        return;
      }

      try {
        results[index] = await tasks[index]();
      } catch (error) {
        failed = true;
        throw error;
      }
    }
  }

  const runners = Array.from(
    {
      length: Math.min(
        concurrency,
        tasks.length
      ),
    },
    runner
  );

  await Promise.all(runners);

  return results;
}