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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 | 162x 74x 74x 162x 74x 74x 162x 162x | import { useState, useEffect } from "react";
function useLocalStorage<T = unknown>(
key: string,
initialValue?: T | (() => T),
): [T, (value: T | ((prevValue: T) => T)) => void] {
// use a function to initialize the state to ensure init only runs on first render
const [storedValue, setStoredValue] = useState<T>(() => {
const item = window.localStorage.getItem(key);
return item
? JSON.parse(item)
: initialValue instanceof Function
? initialValue()
: initialValue;
});
// when state changes update local storage
useEffect(() => {
setTimeout(() => {
window.localStorage.setItem(key, JSON.stringify(storedValue));
}, 0); // delay the write to let React do its job first
}, [key, storedValue]);
// same API as useState so we have to accept a function as argument
const setValue = (value: T | ((prevValue: T) => T)): void => {
const valueToStore = value instanceof Function ? value(storedValue) : value;
setStoredValue(valueToStore);
};
return [storedValue, setValue];
}
export default useLocalStorage;
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