React Hooks 核心用法

Hooks 改变了 React 的编写方式。## useState 状态管理const [count, setCount] = useState(0);## useEffect 副作用useEffect(() => { document.title = count; return () => { cleanup };}, [count]);## useContext 全局状态const theme = useContext(ThemeContext);## useReducer 复杂状态const [state, dispatch] = useReducer(reducer, initialState);## 自定义 Hookfunction useLocalStorage(key, initialValue) { const [value, setValue] = useState(() => { return localStorage.getItem(key) || initialValue; }); return [value, setValue];}## 使用规则- 只在顶层调用 Hook- 只在 React 函数中调用- 依赖数组要完整掌握 Hooks，写出更简洁的 React 组件！