Powerful trick to batch promises using Async Generators

batch-tasks.ts

/**
 * A fuction that returns a Promise
 * @typedef {(<T = any>() => Promise<T>)} Task
 */

/**
 *
 * @param {Array<Task>} tasks
 */
export async function* batchTasks(tasks, limit, taskCallback = (r) => r) {
  // iterate over tasks
  for (let i = 0; i < tasks.length; i = i + limit) {
    // grab the batch of tasks for current iteration
    const batch = tasks.slice(i, i + limit);
    // wait for them to resolve concurrently
    const result = await Promise.all(
      // optionally attach callback to perform any side effects  
      batch.map((task) => task().then((r) => taskCallback(r)))
    );
    // yield the batched result and let consumer know
    yield result;
  }
}