React Loading State Pattern using Toast & SWR

Introduction

Managing the react loading state can be a bit annoying, we need to set it to isLoading before fetching, then set it back to false after it is done. Then we also need to set it up to the button so we can show the loading state, or give some text as an indicator.

Here is what it looks like with the common loading pattern:

const [pokemon, setPokemon] = React.useState<Array<Pokemon>>();
const [isLoading, setIsLoading] = React.useState<boolean>(false);
 
const getData = () => {
  setIsLoading(true);
 
  axios
    .get<PokemonList>('https://pokeapi.co/api/v2/pokemon?limit=20')
    .then((res) => {
      setPokemon(res.data.results);
    })
    .finally(() => setIsLoading(false));
};
 
return <button disabled={isLoading}>{isLoading ? 'loading' : 'fetch'}</button>;

it is annoying to do, and we didn't even cover error state yet.

What should we manage in a loading process?

When we are fetching data, we need to do some things so the waiting experience can be more bearable. Here are some things that we can do:

Loading indicator

Users need to know when their application is in a loading state. This is important so they are not blankly waiting, and get the mindset that they should wait for a bit.

Loading indicator can be a spinner, normal text, some animations, or toast.

Success indicator

We need to tell the user if the loading has succeeded, so they can continue with their work.

Error indicator

When the data fetching goes wrong, we have to let the user know about it.

Blocking action

A common example is when we are submitting a form, we don't want the user to submit twice. We can do that by disabling the button when there is a loading state going on.

Another example is blocking the modal close button when loading, so the user doesn't accidentally close it.

The easy way

I found that this pattern is the most hassle-free, and we can use custom hooks to grab the loading state.

Here is what we are going to build:

Video Description:

getData button is clicked, then there is a loading toast showing.
When it is loading, the button is disabled and showing a loading spinner
After 2 seconds, the loading toast turns into an error toast
getData button is clicked again, then there is a loading toast showing
After 2 seconds, the loading toast turns into a success toast, then all the data loads correctly

ps: the wait cursor is kind of weird in the recording.

With this pattern, we get all 4 things covered, easily.

We get the loading state using toast
We can show error indicator and show the error message from the API
We can show success indicator
Last, all buttons are disabled.

We are using React Hot Toast for the loading, success, and error indicator. All of it are managed only using 1 wrapper function like this:

toast.promise(
  axios
    .get<PokemonList>('https://pokeapi.co/api/v2/pokemon?limit=20')
    .then((res) => {
      setPokemon(res.data.results);
    }),
  {
    loading: 'Loading...',
    success: 'Data fetched successfully',
    error: (err: any) =>
      err?.response?.data?.msg ?? 'Something is wrong, please try again',
  }
);

Configuration

First, we need to install the react-hot-toast

yarn add react-hot-toast

I'm using Next.js for the demo, but the config for CRA is basically the same. Add this to the _app.tsx

import { AppProps } from 'next/app';
 
import '@/styles/globals.css';
 
import DismissableToast from '@/components/DismissableToast';
 
function MyApp({ Component, pageProps }: AppProps) {
  return (
    <>
      <DismissableToast />
      <Component {...pageProps} />
    </>
  );
}
 
export default MyApp;

I added a dismiss button because it doesn't have it by default, you can grab the DismissableToast code from my library.

Usage

Let's say we want to fetch data on mount from an external API using Axios.

We just need to wrap the axios call with the toast function.

React.useEffect(() => {
  toast.promise(
    axios
      .get<PokemonList>('https://pokeapi.co/api/v2/pokemon?limit=20')
      .then((res) => {
        setPokemon(res.data.results);
      }),
    {
      loading: 'Loading...',
      success: 'Data fetched successfully',
      error: (err: any) =>
        err?.response?.data?.msg ?? 'Something is wrong, please try again',
    }
  );
}, []);

That's it! The toast will show status when loading, and when it is a success or an error.

Further Reusablity

You can compose it even more by declaring the defaultToastMessage, then overriding it if you need to.

export const defaultToastMessage = {
  loading: 'Loading...',
  success: 'Data fetched successfully',
  // you can type this with axios error
  // eslint-disable-next-line @typescript-eslint/no-explicit-any
  error: (err: any) =>
    err?.response?.data?.msg ?? 'Something is wrong, please try again',
};
 
toast.promise(axios, {
  ...defaultToastMessage,
  loading: 'Override loading',
});

Accessing loading state

Now, what if we want to get that loading state to disable a button?

We can do that with toast API that I wrapped in a custom hook.

import { useToasterStore } from 'react-hot-toast';
 
/**
 * Hook to get information whether something is loading
 * @returns true if there is a loading toast
 * @example const isLoading = useLoadingToast();
 */
export default function useLoadingToast(): boolean {
  const { toasts } = useToasterStore();
  const isLoading = toasts.some((toast) => toast.type === 'loading');
  return isLoading;
}

And we can use it just like this

const isLoading = useLoadingToast();
 
<button disabled={isLoading}></button>;

With the isLoading state, the rest is all your creativity, you can show some skeleton, change the loading text, give loading spinners, anything you like.

Gotcha: 2 Axios Calls

If you got 2 axios calls, you can chain the next axios call, and add another then to get the value.

toast.promise(
  axios
    .post('/user/login', data)
    .then((res) => {
      const { jwt: token } = res.data.data;
      tempToken = token;
      localStorage.setItem('token', token);
 
      // chaining axios in 1 promise
      return axios.get('/user/get-user-info');
    })
    .then((user) => {
      const role = user.data.data.user_role;
      dispatch('LOGIN', { ...user.data.data, token: tempToken });
 
      history.replace('/');
    }),
  {
    ...defaultToastMessage,
  }
);

SWR Integration

Using SWR to fetch data is even more awesome because we only need to show the loading state on the first fetch. Here is the demo:

Video Description:

First time visited, a loading toast is shown then turns into success toast.
When visited for the second time, there is no loading toast and the data is prefilled with cache.

This is the syntax of SWR:

const { data, error } = useSWR<PokemonList>(
  'https://pokeapi.co/api/v2/pokemon?limit=20'
);

Hmm, this is not a promise, how do we use the toast then?

We can use another custom hook ✨

I made this hook so we can wrap the useSWR just like the toast.promise function.

useWithToast for SWR

import * as React from 'react';
import toast from 'react-hot-toast';
import { SWRResponse } from 'swr';
 
import { defaultToastMessage } from '@/lib/helper';
 
import useLoadingToast from '@/hooks/useLoadingToast';
 
type OptionType = {
  runCondition?: boolean;
  loading?: string;
  success?: string;
  error?: string;
};
 
export default function useWithToast<T, E>(
  swr: SWRResponse<T, E>,
  { runCondition = true, ...customMessages }: OptionType = {}
) {
  const { data, error } = swr;
 
  const toastStatus = React.useRef<string>(data ? 'done' : 'idle');
 
  const toastMessage = {
    ...defaultToastMessage,
    ...customMessages,
  };
 
  React.useEffect(() => {
    if (!runCondition) return;
 
    // if toastStatus is done,
    // then it is not the first render or the data is already cached
    if (toastStatus.current === 'done') return;
 
    if (error) {
      toast.error(toastMessage.error, { id: toastStatus.current });
      toastStatus.current = 'done';
    } else if (data) {
      toast.success(toastMessage.success, { id: toastStatus.current });
      toastStatus.current = 'done';
    } else {
      toastStatus.current = toast.loading(toastMessage.loading);
    }
 
    return () => {
      toast.dismiss(toastStatus.current);
    };
  }, [
    data,
    error,
    runCondition,
    toastMessage.error,
    toastMessage.loading,
    toastMessage.success,
  ]);
 
  return { ...swr, isLoading: useLoadingToast() };
}

In addition, I added the isLoading to the return so we don't need to call the useLoadingToast hooks anymore

Usage

const { data: pokemonData, isLoading } = useWithToast(
  useSWR<PokemonList>('https://pokeapi.co/api/v2/pokemon?limit=20')
);

Awesome, it's looking good and clean.

You can still override the toast messages just like this

const { data: pokemonData, isLoading } = useWithToast(
  useSWR<PokemonList>('https://pokeapi.co/api/v2/pokemon?limit=20'),
  {
    loading: 'Override Loading',
  }
);

Conclusion

I hope this can add to your pattern collection.

You can look at the demo source code on github, but keep in mind there is additional promise to delay the loading time.

React Loading State Pattern using Toast & SWR

Introduction

What should we manage in a loading process?

Loading indicator

Success indicator

Error indicator

Blocking action

The easy way

Configuration

Usage

Further Reusablity

Accessing loading state

Gotcha: 2 Axios Calls

SWR Integration

useWithToast for SWR

Usage

Conclusion

Other posts that you might like

Advanced React Patterns

How to Create Fully Reusable React Components

A look at React hydration and pre-rendered HTML

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