Trying Lazy Loading and getting flicker?

Hey ya'll! Using suspense + lazy for the first time, would really really appreciate some help.

I've recently enabled suspense and lazy loading in my application, and when I apply them to my <Router>, I get a solid load + performance boost.

Was wondering though, in-between clicking on pages, I get this huge white flicker. I'm using it like so:

import React, { Suspense, lazy } from 'react';
import { BrowserRouter as Router, Route, Switch, Redirect } from 'react-router-dom';
{...}

const NotFound = lazy(() => import('./components/NotFound'));
const Feed = lazy(() => import('./components/Feed'));
const Food = lazy(() => import('./components/Food'));
{...}
import('./components/DEBUGEasyPeasyContents'));

const App: React.SFC = () => {
    const isLoggedIn = useStoreState(state => state.userModel.isLoggedIn);

    const Spinner = <Spin size="large" style={{ width: '100%', margin: 'auto', padding: '10%' }} />;

    return (
        <>
            <ReactNotification />
            <Router>
                <Suspense fallback={wrapHOC(Spinner)}>
                    <Switch>
                        {isLoggedIn && (
                            <>
                                <Route path="/login" exact={true} component={Login} />
                                <Route path="/changePassword" exact={true} component={wrapHOC(ChangePassword)} />
                                <Route path="/account" exact={true} component={wrapHOC(AccountInfo)} />
                                <Route path="/dashboard" exact={true} component={wrapHOC(Dashboard)} />
                            {...}
                    </Switch>
                </Suspense>
            </Router>
        </>
    );
};

export default App;

In-between clicking on pages, the whole page flashes white for like 1.3ms according to the chrome screenshot inspector. It ruins the performance boost for me, so I'm desperate to figure out the cause.

Any advice appreciated, thanks!

Comments

[Si]

Throttle your speed to like Slow 3G or something, and see if you can capture what the white background is.

Is it displaying a loading screen, which flickers because it loads so quickly?

[Ben Mitchinson]

It does! How do I avoid this? I was hoping my spinner would be rendered without a flash? It doesn't even render my spinner during this time it's only white.

[Si]

It's "flashing" because you're page is loading too quickly, so the spinner loads and then disappears because the job is over.

I'm not a frontend dev, or a designer, but I would find a loading mechanism that doesn't cause a flash.

For example, a skeleton screen.

[Gleb Irovich]

Hey! You see flickering because loading happens too fast and spinner changes immediately to the route content. You can try setting a minimal delay, since lazy can return regular Promise.

const Food = lazy(() => Promise.all([
  import('./components/Food'),
  new Promise((resolve) => setTimeout(resolve, 3000)) // ensures minimal delay
 ]).then(([module]) => module)
);

or create a function out of it, which would reduce the boilerplate:

const lazyDelayed = (path: string, delay = 3000) => {
  return lazy(() => Promise.all([
    import(path),
    new Promise((resolve) => setTimeout(resolve, delay)) // ensures minimal delay
  ]).then(([module]) => module));
}

const Food = lazyDelayed('./components/Food')

[Ben Mitchinson]

@gleb Thanks for this suggestion, it's behaving like you described "loading happens too fast and spinner changes immediately to the route content"

I tried your solution, and it added a delay to the load, where the white screen was extended by 3 seconds, then went to the component. Did you get this solution from here? stackoverflow.com/questions/541589...

I'm still don't understand the difference between the first and second solutions listed there in that SO post. Tried both to no avail.

I'll try to create something reproducible in typescript create-react-app.

[Gleb Irovich]

Here is a short working demo:
github.com/GlebIrovich/suspense-demo

I think something is wrong with the HOC. Because if you look at my implementation, valid Route can only accept HOC like a that: <Route path="/changePassword" exact={true} component={() => withHOC(LazyContent)} />

Hope it helps

[Gleb Irovich]

Regarding the solution on SO.
First one adds time on top of the time required for import. So if import takes 2 sec and delay is 3 sec, totally it will take 5 sec.
The second approach uses Promise.all, which makes the same work "in parallel". So if import takes 2 sec and delay is 3 sec, totally it will take 3 sec. So the operation will take AT LEAST the time specified in the delay.

[Gleb Irovich]

I would suspect then that your HOC not returning properly. Could you validate if spinner is shown without using hoc?

[Vinay Sharma]

Hi Gleb, creating a reusable function results in the following error:

Error: Cannot find module './Home'