@atlaskit/pragmatic-drag-and-drop-react-beautiful-dnd-migration/dist/es2019/drag-drop-context/use-scheduler.js

An optional Pragmatic drag and drop package that enables rapid migration from react-beautiful-dnd to Pragmatic drag and drop

import { useState } from 'react';
import { batchUpdatesForReact16 } from '../utils/batch-updates-for-react-16';
const idleQueue = {
  status: 'idle'
};
function createScheduler() {
  let queue = idleQueue;
  const schedule = callback => {
    /**
     * If the queue is currently idle (no update scheduled) then
     * we should call `setTimeout` to schedule an update.
     */
    if (queue.status === 'idle') {
      queue = {
        status: 'pending',
        timeoutId: setTimeout(flush, 0),
        items: []
      };
    }
    queue.items.push(callback);
  };
  const flush = () => {
    if (queue.status === 'idle') {
      return;
    }

    /**
     * Clearing the timeout optimistically in case `flush` was called directly.
     */
    clearTimeout(queue.timeoutId);
    /**
     * A shallow copy is used so that updates which queue further updates
     * are not batched together. This is to more closely match rbd.
     */
    const items = Array.from(queue.items);
    /**
     * The queue is made idle so it is ready to schedule further updates.
     */
    queue = idleQueue;

    /**
     * Scheduled callbacks are batched.
     *
     * The batching is more evident when the page is running more slowly.
     */
    batchUpdatesForReact16(() => {
      items.forEach(callback => callback());
    });
  };
  return {
    schedule,
    flush
  };
}

/**
 * Used to schedule callbacks inside of a `setTimeout(fn, 0)`.
 *
 * This is used to match the behavior and timings of `react-beautiful-dnd`.
 */
export function useScheduler() {
  const [scheduler] = useState(createScheduler);
  return scheduler;
}