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useAsync react Code Snippet in 2022

hooksstatereduceradvanced

Last Updated: 25 September 2022

Handles asynchronous calls.

  • Create a custom hook that takes a handler function, fn.
  • Define a reducer function and an initial state for the custom hook's state.
  • Use the useReducer() hook to initialize the state variable and the dispatch function.
  • Define an asynchronous run function that will run the provided callback, fn, while using dispatch to update state as necessary.
  • Return an object containing the properties of state (value, error and loading) and the run function.
const useAsync = fn => { const initialState = { loading: false, error: null, value: null }; const stateReducer = (_, action) => { switch (action.type) { case 'start': return { loading: true, error: null, value: null }; case 'finish': return { loading: false, error: null, value: action.value }; case 'error': return { loading: false, error: action.error, value: null }; } }; const [state, dispatch] = React.useReducer(stateReducer, initialState); const run = async (args = null) => { try { dispatch({ type: 'start' }); const value = await fn(args); dispatch({ type: 'finish', value }); } catch (error) { dispatch({ type: 'error', error }); } }; return { ...state, run }; };
const RandomImage = props => { const imgFetch = useAsync(url => fetch(url).then(response => response.json()) ); return ( <div> <button onClick={() => imgFetch.run('https://dog.ceo/api/breeds/image/random')} disabled={imgFetch.isLoading} > Load image </button> <br /> {imgFetch.loading && <div>Loading...</div>} {imgFetch.error && <div>Error {imgFetch.error}</div>} {imgFetch.value && ( <img src={imgFetch.value.message} alt="avatar" width={400} height="auto" /> )} </div> ); }; ReactDOM.render(<RandomImage />, document.getElementById('root'));

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