React suspense/lazy delay?

Question

I am trying to use the new React Lazy and Suspense to create a fallback loading component. This works great, but the fallback is showing only a few ms. Is there a way to add an additional delay or minimum time, so I can show animations from this component before the next component is rendered?

Lazy import now

const Home = lazy(() => import("./home"));
const Products = lazy(() => import("./home/products"));

Waiting component:

function WaitingComponent(Component) {

    return props => (
      <Suspense fallback={<Loading />}>
            <Component {...props} />
      </Suspense>
    );
}

Can I do something like this?

const Home = lazy(() => {
  setTimeout(import("./home"), 300);
});

Answer 1

lazy function is supposed to return a promise of { default: ... } object which is returned by import() of a module with default export. setTimeout doesn't return a promise and cannot be used like that. While arbitrary promise can:

const Home = lazy(() => {
  return new Promise(resolve => {
    setTimeout(() => resolve(import("./home")), 300);
  });
});

If an objective is to provide minimum delay, this isn't a good choice because this will result in additional delay.

A minimum delay would be:

const Home = lazy(() => {
  return Promise.all([
    import("./home"),
    new Promise(resolve => setTimeout(resolve, 300))
  ])
  .then(([moduleExports]) => moduleExports);
});