Function register

packages/next/src/client/index.tsx:273–274

([r, f])

  pageLoader = new PageLoader(initialData.buildId, prefix)

  const register: RegisterFn = ([r, f]) =>
    pageLoader.routeLoader.onEntrypoint(r, f)
  if (window.__NEXT_P) {
    // Defer page registration for another tick. This will increase the overall
    // latency in hydrating the page, but reduce the total blocking time.