next.js/packages/next/src/client/request-idle-callback.ts

export const requestIdleCallback =
  (typeof self !== 'undefined' &&
    self.requestIdleCallback &&
    self.requestIdleCallback.bind(window)) ||
  function (cb: IdleRequestCallback): number {
    let start = Date.now()
    return self.setTimeout(function () {
      cb({
        didTimeout: false,
        timeRemaining: function () {
          return Math.max(0, 50 - (Date.now() - start))
        },
      })
    }, 1)
  }

export const cancelIdleCallback =
  (typeof self !== 'undefined' &&
    self.cancelIdleCallback &&
    self.cancelIdleCallback.bind(window)) ||
  function (id: number) {
    return clearTimeout(id)
  }