nextjs getServerSideProps show loading

Question

I am using getServerSideProps in pages/post/index.js:

import React from "react";
import Layout from "../../components/Layout";

function Post({ post }) {
  console.log("in render", post);
  return (
    <Layout title={post.name}>
      <pre>{JSON.stringify(post, undefined, 2)}</pre>
    </Layout>
  );
}

export async function getServerSideProps({ query }) {
  return fetch(
    `${process.env.API_URL}/api/post?id=${query.id}`
  )
    .then(result => result.json())
    .then(post => ({ props: { post } }));
}

export default Post;

When I directly load /post/2 it works as expected but when I go from /posts to /post/2 by clicking on a link:

<Link
  as={`/post/${post.id}`}
  href={`/post?id=${post.id}`}
>

It looks like nothing happens for 2 seconds (the api delay) and then the content shows. I can see in the network tab that _next/data/development/post/9.json is being loaded by fetchNextData.

I would like to show a loading spinner when I move from one route to another using next/Link but I can't find any documentation on getServerSideProps that allows me to do this.

When I directly go to /post/:id I'd like the data to be fetched server side and get a fully rendered page (works) but when I then move to another route the data should be fetched from the client (works). However; I would like to have a loading indicator and not have the UI freeze up for the duration of the data request.

Answer 1

Here is an example using hooks.

pages/_app.js

    import Router from "next/router";

    export default function App({ Component, pageProps }) {
      const [loading, setLoading] = React.useState(false);
      React.useEffect(() => {
        const start = () => {
          console.log("start");
          setLoading(true);
        };
        const end = () => {
          console.log("finished");
          setLoading(false);
        };
        Router.events.on("routeChangeStart", start);
        Router.events.on("routeChangeComplete", end);
        Router.events.on("routeChangeError", end);
        return () => {
          Router.events.off("routeChangeStart", start);
          Router.events.off("routeChangeComplete", end);
          Router.events.off("routeChangeError", end);
        };
      }, []);
      return (
        <>
          {loading ? (
            <h1>Loading...</h1>
          ) : (
            <Component {...pageProps} />
          )}
        </>
      );
    }

Answer 2

You can use nprogress in your _app.js

import NProgress from 'nprogress';
import "nprogress/nprogress.css";
import Router from 'next/router';

NProgress.configure({
  minimum: 0.3,
  easing: 'ease',
  speed: 800,
  showSpinner: false,
});

Router.events.on('routeChangeStart', () => NProgress.start());
Router.events.on('routeChangeComplete', () => NProgress.done());
Router.events.on('routeChangeError', () => NProgress.done());

or dynamic import to _app.js to reduce bundle size

ProgessBar.js

import Router from 'next/router';
import NProgress from 'nprogress';
import "nprogress/nprogress.css";

NProgress.configure({
    minimum: 0.3,
    easing: 'ease',
    speed: 500,
    showSpinner: false,
});

Router.events.on('routeChangeStart', () => NProgress.start());
Router.events.on('routeChangeComplete', () => NProgress.done());
Router.events.on('routeChangeError', () => NProgress.done());

export default function () {
    return null;
}

_app.js

import dynamic from 'next/dynamic';
const ProgressBar = dynamic(() => import('components/atoms/ProgressBar'), { ssr: false });

const App = () => {
   ...
   return <>
       ...
       <ProgressBar />
   </>
}

Ps: If you want to change color of progress bar, you can override in global css, something like this

#nprogress .bar {
    background: #6170F7 !important;
    height: 3px !important;
}

Answer 3

How about simply adding a component level loading state to Post (vs. adding a loader on App Level for every route change since some route changes might not require server side rendering).

Setting the isLoading state to true when the relevant query param changes, in this case the post id, and setting the state to false once the props, in this case the post data, updated.

Along these lines:

pages/post/index.js:

import React from "react";
import Layout from "../../components/Layout";
import { useRouter } from 'next/router';

function Post({ post }) {
  const router = useRouter();
  const [isLoading, setIsLoading] = useState(false);
  
  // loading new post
  useEffect(()=> {
   setIsLoading(true);
  }, [router.query?.id]);
  
  // new post loaded
  useEffect(()=> {
   setIsLoading(false)
  }, [post]);

  return (
    <>
    {isLoading ? (
      <h1>Loading...</h1>
     ) : (
      <Layout title={post.name}>
       <pre>{JSON.stringify(post, undefined, 2)}</pre>
      </Layout>
    )}
    </> 
  );
}

export async function getServerSideProps({ query }) {
  return fetch(
    `${process.env.API_URL}/api/post?id=${query.id}`
  )
    .then(result => result.json())
    .then(post => ({ props: { post } }));
}

export default Post;

Answer 4

You can create a custom hook:

usePageLoading.ts

import Router from 'next/router';
import { useEffect, useState } from 'react';

export const usePageLoading = () => {
  const [isPageLoading, setIsPageLoading] = useState(false);

  useEffect(() => {
    const routeEventStart = () => {
      setIsPageLoading(true);
    };
    const routeEventEnd = () => {
      setIsPageLoading(false);
    };

    Router.events.on('routeChangeStart', routeEventStart);
    Router.events.on('routeChangeComplete', routeEventEnd);
    Router.events.on('routeChangeError', routeEventEnd);
    return () => {
      Router.events.off('routeChangeStart', routeEventStart);
      Router.events.off('routeChangeComplete', routeEventEnd);
      Router.events.off('routeChangeError', routeEventEnd);
    };
  }, []);

  return { isPageLoading };
};

and then inside your App component use it: _app.js

import Router from "next/router";
import { usePageLoading } from './usePageLoading';

export default function App({ Component, pageProps }) {
  const { isPageLoading } = usePageLoading();

  return (
    <>
      {isPageLoading ? (
        <h1>Loading...</h1>
      ) : (
        <Component {...pageProps} />
      )}
    </>
   );
}