如何将本地存储中的计时器值减一?使用了“useLocalStorage”钩子,但该值不会动态减一
计时器本身:
const [timeLeft, setTimeLeft] = useLocalStorage('timer', 5 * 60)
const getPadTime = (time) => time.toString().padStart(2, '0')
const minutes = getPadTime(Math.floor(timeLeft / 60))
const seconds = getPadTime(timeLeft - minutes * 60)
useEffect(() => {
const interval = setInterval(() => {
setTimeLeft((timeLeft) => (timeLeft >= 1 ? timeLeft - 1 : setDisabled() || 5 * 60))
}, 1000)
return () => clearInterval(interval)
}, [])
'useLocalStorage' 挂钩数据:
import {useState} from 'react'
function useLocalStorage(key, initialValue) {
// State to store our value
// Pass initial state function to useState so logic is only executed once
const [storedValue, setStoredValue] = useState(() => {
if (typeof window === "undefined") {
return initialValue;
}
try {
// Get from local storage by key
const item = window.localStorage.getItem(key);
// Parse stored json or if none return initialValue
return item ? JSON.parse(item) : initialValue;
} catch (error) {
// If error also return initialValue
console.log(error);
return initialValue;
}
});
// Return a wrapped version of useState's setter function that ...
// ... persists the new value to localStorage.
const setValue = (value) => {
try {
// Allow value to be a function so we have same API as useState
const valueToStore =
value instanceof Function ? value(storedValue) : value;
// Save state
setStoredValue(valueToStore);
// Save to local storage
if (typeof window !== "undefined") {
window.localStorage.setItem(key, JSON.stringify(valueToStore));
}
} catch (error) {
// A more advanced implementation would handle the error case
console.log(error);
}
};
return [storedValue, setValue];
}
export default useLocalStorage
通过安装 npm 包解决了这个问题
use-local-storage。示例:https ://codesandbox.io/s/zealous-hodgkin-9e76q4?file=/src/App.js