@pirxpilot/nanoscheduler/index.js

Schedule work to be completed when the browser is idle.

import assert from '@pirxpilot/nanoassert';
export default createScheduler;

function createScheduler() {
  if (!globalThis._nanoScheduler) globalThis._nanoScheduler = scheduler();
  return globalThis._nanoScheduler;
}

const method = typeof requestIdleCallback === 'function' ? requestIdleCallback : fallbackRequestIdleCallback;

function scheduler() {
  let scheduled = false;
  const queue = [];
  return { push };

  function push(cb) {
    assert.equal(typeof cb, 'function', 'nanoscheduler.push: cb should be type function');

    queue.push(cb);
    schedule();
  }

  function schedule() {
    if (scheduled) return;

    scheduled = true;

    method(idleDeadline => {
      while (queue.length && idleDeadline.timeRemaining() > 0) {
        const cb = queue.shift();
        cb(idleDeadline);
      }
      scheduled = false;
      if (queue.length) schedule();
    });
  }
}

function fallbackRequestIdleCallback(cb) {
  setTimeout(cb, 0, { timeRemaining: () => 1 });
}