恢复用户的登录状态（Next.js 前端应用开发实践）

After successful business login, user data can be stored in the browser's local storage to maintain user login state upon application refresh.
Two methods are defined: setStorage to set local storage with a key (string) and value (any), and getStorage to retrieve local storage data using a key (string).
setStorage uses localStorage.setItem to save data, with value processed by JSON.stringify.
getStorage may return the data processed by JSON.parse if present or null otherwise.
A constant STORAGE_KEY with currentUser property is exported for consistent data naming during storage and retrieval.
A LoginProvider component utilizes useEffect to react to currentUser changes, storing or retrieving user data as necessary.
Local storage gets tested in the browser's developer tools, demonstrating appearance and retrieval of currentUser data, which includes the user's ID, name, and token.
Upon page refresh and application reload, the saved currentUser data is read from local storage and used to restore the user's login state.
The current user's name is displayed at the top of the page, reflecting the logged-in status.

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