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useEffect
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| useEffect(() => { | |
| let cancelRequest = false; | |
| if (!url) return; | |
| const fetchData = async () => { | |
| dispatch({ type: 'FETCHING' }); | |
| if (cache.current[url]) { | |
| const data = cache.current[url]; | |
| dispatch({ type: 'FETCHED', payload: data }); | |
| } else { | |
| try { | |
| const response = await fetch(url); | |
| const data = await response.json(); | |
| cache.current[url] = data; | |
| if (cancelRequest) return; | |
| dispatch({ type: 'FETCHED', payload: data }); | |
| } catch (error) { | |
| if (cancelRequest) return; | |
| dispatch({ type: 'FETCH_ERROR', payload: error.message }); | |
| } | |
| } | |
| }; | |
| fetchData(); | |
| return function cleanup() { | |
| cancelRequest = true; | |
| }; | |
| }, [url]); |
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