30秒学会 React 片段 – React useLocalStorage hook

Creates a stateful value that is persisted to localStorage, and a function to update it.

• Use the useState() hook with a function to initialize its value lazily.
• Use a try...catch block and Storage.getItem() to try and get the value from Window.localStorage. If no value is found, use Storage.setItem() to store the defaultValue and use it as the initial state. If an error occurs, use defaultValue as the initial state.
• Define a function that will update the state variable with the passed value and use Storage.setItem() to store it.

代码实现

const useLocalStorage = (keyName, defaultValue) => {
  const [storedValue, setStoredValue] = React.useState(() => {
    try {
      const value = window.localStorage.getItem(keyName);

      if (value) {
        return JSON.parse(value);
      } else {
        window.localStorage.setItem(keyName, JSON.stringify(defaultValue));
        return defaultValue;
      }
    } catch (err) {
      return defaultValue;
    }
  });

  const setValue = newValue => {
    try {
      window.localStorage.setItem(keyName, JSON.stringify(newValue));
    } catch (err) {}
    setStoredValue(newValue);
  };

  return [storedValue, setValue];
};

使用样例

const MyApp = () => {
  const [name, setName] = useLocalStorage('name', 'John');

  return <input value={name} onChange={e => setName(e.target.value)} />;
};

ReactDOM.createRoot(document.getElementById('root')).render(
  <MyApp />
);

翻译自：https://www.30secondsofcode.org/react/s/use-local-storage