batch async

batch.ts

// takes a large array of items, chunks them, performs an async task on that item

import { chunk } from "lodash";

function wait(time: number) { // in ms
  return new Promise(resolve => setTimeout(resolve, time));
}

export async function batch(
  arr: any,
  size: number,
  task: function,
  delay: number = 1000
) {
  const chunks = chunk(arr, size);
  return chunks.reduce(async (previousPromise, nextChunk) => {
    await previousPromise;
    await wait(delay);
    return task(nextChunk);
  }, Promise.resolve());
}


// eg

let allOfSomething = await getAll();

function deleteSomething(group: any) {
    return Promise.all(
      group.map((item: any) => {
        return item.delete();
      })
    );
}

await batch(allOfSomething, 250, deleteSomething);