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import { Dispatch, SetStateAction, useEffect, useState } from 'react' | |
type SetValue<T> = Dispatch<SetStateAction<T>> | |
function useLocalStorage<T>(key: string, initialValue: T): [T, SetValue<T>] { | |
// Get from local storage then | |
// parse stored json or return initialValue | |
const readValue = (): T => { | |
// Prevent build error "window is undefined" but keep keep working | |
if (typeof window === 'undefined') { | |
return initialValue | |
} | |
try { | |
const item = window.localStorage.getItem(key) | |
return item ? (JSON.parse(item) as T) : initialValue | |
} catch (error) { | |
console.warn(`Error reading localStorage key β${key}β:`, error) | |
return initialValue | |
} | |
} | |
// State to store our value | |
// Pass initial state function to useState so logic is only executed once | |
const [storedValue, setStoredValue] = useState<T>(readValue) | |
// Return a wrapped version of useState's setter function that ... | |
// ... persists the new value to localStorage. | |
const setValue: SetValue<T> = value => { | |
// Prevent build error "window is undefined" but keeps working | |
if (typeof window == 'undefined') { | |
console.warn(`Tried setting localStorage key β${key}β even though environment is not a client`) | |
} | |
try { | |
// Allow value to be a function so we have the same API as useState | |
const newValue = value instanceof Function ? value(storedValue) : value | |
// Save to local storage | |
window.localStorage.setItem(key, JSON.stringify(newValue)) | |
// Save state | |
setStoredValue(newValue) | |
// We dispatch a custom event so every useLocalStorage hook are notified | |
window.dispatchEvent(new Event('local-storage')) | |
} catch (error) { | |
console.warn(`Error setting localStorage key β${key}β:`, error) | |
} | |
} | |
useEffect(() => { | |
setStoredValue(readValue()) | |
// eslint-disable-next-line react-hooks/exhaustive-deps | |
}, []) | |
useEffect(() => { | |
const handleStorageChange = () => { | |
setStoredValue(readValue()) | |
} | |
// this only works for other documents, not the current one | |
window.addEventListener('storage', handleStorageChange) | |
// this is a custom event, triggered in writeValueToLocalStorage | |
window.addEventListener('local-storage', handleStorageChange) | |
return () => { | |
window.removeEventListener('storage', handleStorageChange) | |
window.removeEventListener('local-storage', handleStorageChange) | |
} | |
// eslint-disable-next-line react-hooks/exhaustive-deps | |
}, []) | |
return [storedValue, setValue] | |
} | |
export default useLocalStorage | |