507 lines
16 KiB
Markdown
507 lines
16 KiB
Markdown
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---
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tags: [React, TypeScript, Frontend]
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create time: 2026-04-29 22:09
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---
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# TS + React
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## 概述
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TypeScript 为 React 提供编译时类型检查和智能提示，将运行时错误提前到编码阶段。本文档从 Props、State、Hook、Ref 等核心场景切入，逐步深入到泛型推导、区分联合类型和 Schema 校验等进阶模式。
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> [!question] 为什么 React + TS 值得投入？
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>
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> React 本身是纯 JS 库，但大型项目中「谁在改什么数据」「这个函数接收什么参数」往往成为协作瓶颈。TS 让你在写代码时就能获得精确的类型反馈，而不是等到测试环节才发现 `undefined is not a function`。
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## Props 类型定义
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### 基础方式
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```tsx
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// ✅ 方式1：interface（推荐，可 extend）
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interface ButtonProps {
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label: string;
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onClick?: () => void;
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}
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const Button = ({ label, onClick }: ButtonProps) => (
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<button onClick={onClick}>{label}</button>
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);
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// ✅ 方式2：type alias（适合联合类型）
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type ButtonProps = { label: string; onClick?: () => void };
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// ❌ 避免：解构后不标注类型
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function BadComponent({ a, b }) { ... } // a 和 b 都是 any!
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```
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> [!tip] interface vs type —— 何时用哪个？
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>
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> - **优先 interface**：它支持 `extends` / `implements`，更适合组件 Props 的层级扩展
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> - **选 type**：当你需要联合类型 (`A | B`)、交叉类型 (`A & B`) 或映射类型 (`Record<K,V>`) 时
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### 合成事件类型
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```tsx
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// ❌ 不要用 HTML 原生的 Event
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const handleChange = (e: Event) => {};
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// ✅ 使用 React 的合成事件类型
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const handleChange = (e: React.ChangeEvent<HTMLInputElement>) => {
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e.target.value; // string | number | string[]（取决于 input type）
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};
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const handleSubmit = (e: React.FormEvent<HTMLFormElement>) => {
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e.preventDefault(); // 阻止表单默认提交
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};
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const handleClick = (e: React.MouseEvent<HTMLButtonElement>) => {
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console.log(e.button); // 0=左键, 1=中键, 2=右键
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};
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const handleKeyDown = (e: React.KeyboardEvent<HTMLInputElement>) => {
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if (e.key === "Enter") submit();
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};
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```
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> [!warning] 常见误区：syntheticEvent 的池化问题
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>
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> React 17 之前合成事件会被复用（池化），异步访问时可能已被清空。在 `setTimeout` 或 Promise 回调中，请先读取到局部变量：
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> ```tsx
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> const value = e.target.value; // 先取值
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> setTimeout(() => console.log(value), 100);
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> ```
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### Children 类型
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```tsx
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// 通用 children —— 接受任意合法 React 节点
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function Card({ children }: { children: React.ReactNode }) {}
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// 严格类型 children —— 限制允许的子节点类型
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interface TabsProps {
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children: React.ReactElement<TabProps>; // 只能是 Tab 组件
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}
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// 泛型 children —— 子节点携带的数据类型可参数化
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interface ListProps<T> {
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children: React.ReactElement<{ item: T }> [];
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}
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```
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## State 类型推导
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### useState
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```tsx
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interface User { name: string; role: "admin" | "user"; age: number }
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// 完整泛型
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const [user, setUser] = useState<User>({ name: "", role: "user", age: 0 });
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// 可选初始值 —— 必须显式声明联合类型
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const [user, setUser] = useState<User | null>(null);
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// 使用时需判空
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user?.name; // ✅ 可选链，安全
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(user as User).name; // or: 类型断言
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user!?.name; // non-null assertion（慎用）
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```
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> [!tip] 利用构造函数推断
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>
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> 当 initialState 是个对象字面量时，可以用类构造函数的模式让 TS 自动推导出 State 类型，减少重复书写：
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> ```tsx
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> class UserStore {
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> name = "";
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> role: "admin" | "user" = "user";
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> age = 0;
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> }
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> const [user, setUser] = useState(new UserStore());
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> // 注意：这里 user 类型就是 new UserStore() 的实例类型
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> ```
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### useReducer
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```tsx
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interface State { items: Item[]; filter: string }
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type Action =
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| { type: "SET_FILTER"; payload: string }
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| { type: "ADD_ITEM"; payload: Item };
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function reducer(state: State, action: Action): State {
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switch (action.type) {
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case "SET_FILTER": return { ...state, filter: action.payload };
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case "ADD_ITEM": return { ...state, items: [...state.items, action.payload] };
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}
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}
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const [state, dispatch] = useReducer(reducer, initialState);
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```
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## Ref 类型定义
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### useRef
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```tsx
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// 元素 ref —— 最常用
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const inputRef = useRef<HTMLInputElement>(null);
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// mutable value ref（不触发 re-render）
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const timerIdRef = useRef<ReturnType<typeof setInterval>>(undefined);
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timerIdRef.current = setInterval(() => {}, 1000);
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// class component style ref object（用于挂载子组件引用）
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const childRef = useRef<ComponentInstance>(null);
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// 需要 useImperativeHandle 暴露方法给父级
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```
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> [!example] 为什么 ref.current 改变不会触发渲染？
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>
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> React 的更新机制只响应 setState 调用。ref 的设计初衷就是绕过 React 的响应式系统——比如在 useEffect 中保存上一次 props 的值、存储定时器 ID、或者调用子组件的原生 DOM API。如果你发现修改 ref 后需要 UI 同步更新，说明你可能应该用 state。
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### forwardRef + useImperativeHandle
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```tsx
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const FancyInput = forwardRef<HTMLInputElement, { label: string }>(
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function FancyInput(props, ref) {
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const innerRef = useRef<HTMLInputElement>(null);
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// 只暴露 focus 和 blur 给父组件，隐藏其他原生方法
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useImperativeHandle(ref, () => ({
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focus: () => innerRef.current?.focus(),
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blur: () => innerRef.current?.blur(),
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}));
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return <input ref={innerRef} label={props.label} />;
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}
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);
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```
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## Hook 类型推导
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### 自定义 Hook 返回值
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```tsx
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interface UseCountReturn {
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count: number;
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increment: () => void;
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decrement: () => void;
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}
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function useCount(initial = 0): UseCountReturn {
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const [count, setCount] = useState(initial);
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return {
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count,
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increment: () => setCount(c => c + 1),
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decrement: () => setCount(c => c - 1),
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};
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}
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```
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> [!tip] 让返回值类型自动推导
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>
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> 如果不想手动编写返回类型接口，可以借助 TypeScript 4.7+ 的 `as const` 技巧或使用 `ReturnType` 工具类型：
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> ```tsx
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> function useMouse() {
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> const [pos, setPos] = useState({ x: 0, y: 0 });
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> useEffect(() => { /* ... */ }, []);
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> return pos; // TS 会自动推导出 { readonly x: number; readonly y: number }
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> }
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> ```
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### 泛型 Hook —— 最强大的类型推导场景
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```tsx
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function useAsync<T, Args extends any[]>(
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asyncFn: (...args: Args) => Promise<T>,
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deps: DependencyList
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): { data: T | null; loading: boolean; error: Error | null; invoke: (...args: Args) => void } {
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const [data, setData] = useState<T | null>(null);
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const [loading, setLoading] = useState(false);
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const [error, setError] = useState<Error | null>(null);
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const invoke = useCallback(async (...args: Args) => {
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setLoading(true);
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setError(null);
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try {
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const result = await asyncFn(...args);
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setData(result);
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} catch (err) {
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setError(err as Error);
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} finally {
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setLoading(false);
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}
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}, [asyncFn, ...deps]);
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useEffect(() => { invoke(); }, [invoke]);
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return { data, loading, error, invoke };
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}
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// T 自动推导！无需手动指定
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const { data: users } = useAsync(fetchUsers, []); // data: User[] | null
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const { data: user } = useAsync(fetchUserById, [id]); // data: User | null
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const { data: config } = useAsync(fetchConfig, [env]); // data: Config | null
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```
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> [!question] 为什么 `Args extends any[]`？
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>
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> 这让我们可以同时参数化「异步函数的返回值类型」和「异步函数的入参」。例如 `fetchUserById(id: string)` 的 `T = User`，`Args = [string]`，类型信息从内到外全自动推导，不需要在调用处再次声明。
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## discriminated Union（区分联合类型）
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```tsx
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interface SuccessAction { type: "success"; data: User[] }
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interface ErrorAction { type: "error"; error: string }
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interface LoadingAction { type: "loading" }
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type Action = SuccessAction | ErrorAction | LoadingAction;
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function reducer(state: State, action: Action): State {
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switch (action.type) {
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case "success":
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return { ...state, data: action.data, status: "loaded" };
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// ✅ TS 自动推断 action.data 是 User[]
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case "error":
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return { ...state, error: action.error };
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// ✅ TS 自动推断 action.error 是 string
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case "loading":
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return { ...state, status: "loading" };
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}
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}
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```
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> [!important] exhaustive check 防漏分支
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>
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> 添加一个 `default` 分支并用 `never` 类型确保所有联合成员都被覆盖：
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> ```tsx
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> function reducer(state: State, action: Action): State {
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> switch (action.type) {
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> case "success": return { ...state, status: "loaded" };
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> case "error": return { ...state, status: "failed" };
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> case "loading": return { ...state, status: "pending" };
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> default:
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> const _exhaustiveCheck: never = action;
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> throw new Error(`Unhandled action type: ${_exhaustiveCheck}`);
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> }
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> }
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> ```
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> 一旦新增了一个 Action 类型但没有在 switch 中处理，TS 编译器会立刻报错。
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```mermaid
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graph LR
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A["Union Type"] -->|"switch on type field"| B["Type Narrowing"]
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B --> C["discriminated union — 最优解"]
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B --> D["typeof check"]
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B --> E["in operator"]
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B --> F["instanceof check"]
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style C fill:#61DAFB,color:#000
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style A fill:#fff,color:#000
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```
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## Context 类型定义
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```tsx
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interface ThemeContextType {
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theme: "light" | "dark";
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toggleTheme: () => void;
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}
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// 创建 context 时传入默认值（可为 null，配合非空断言使用）
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const ThemeContext = createContext<ThemeContextType | null>(null);
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// 封装类型安全的消费 Hook —— 比直接 useContext 更安全
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function useTheme(): ThemeContextType {
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const ctx = useContext(ThemeContext);
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if (!ctx) throw new Error("useTheme must be used within ThemeProvider");
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return ctx;
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}
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// Provider 类型 —— 将 value 的类型与 Context 绑定
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function ThemeProvider({ children }: { children: React.ReactNode }) {
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const [theme, setTheme] = useState<"light" | "dark">("light");
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return (
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<ThemeContext.Provider value={{ theme, toggleTheme: () => setTheme(t => t === "light" ? "dark" : "light") }}>
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{children}
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</ThemeContext.Provider>
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);
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}
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```
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> [!tip] 多 Context 时的组合策略
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>
|
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|
|
> Context 数量增多后，推荐使用 **多个小型 Context** 而非一个巨型 Context：每个 Context 负责一小块职责（认证、主题、语言），这样消费者只会在自己关注的 context 变化时重渲染。也可以用一个 Context 包裹另一个，形成嵌套结构。
|
|||
|
|
|
|||
|
|
## 泛型组件与 Polymorphic Components
|
|||
|
|
|
|||
|
|
### 泛型列表组件
|
|||
|
|
|
|||
|
|
```tsx
|
|||
|
|
interface SelectableTableProps<T> {
|
|||
|
|
data: T[];
|
|||
|
|
renderRow: (item: T, selected: boolean) => React.ReactNode;
|
|||
|
|
selectedIds: Set<string>;
|
|||
|
|
onSelect: (id: string) => void;
|
|||
|
|
getId: (item: T) => string;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
function SelectableTable<T>({
|
|||
|
|
data, renderRow, selectedIds, onSelect, getId,
|
|||
|
|
}: SelectableTableProps<T>) {
|
|||
|
|
return (
|
|||
|
|
<table>
|
|||
|
|
<tbody>
|
|||
|
|
{data.map(item => {
|
|||
|
|
const id = getId(item);
|
|||
|
|
const selected = selectedIds.has(id);
|
|||
|
|
return <tr key={id} onClick={() => onSelect(id)}>
|
|||
|
|
<td>{renderRow(item, selected)}</td>
|
|||
|
|
</tr>;
|
|||
|
|
})}
|
|||
|
|
</tbody>
|
|||
|
|
</table>
|
|||
|
|
);
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// 使用：T 自动推导为 User
|
|||
|
|
<SelectableTable
|
|||
|
|
data={users}
|
|||
|
|
getId={(u: User) => u.id}
|
|||
|
|
renderRow={(u, sel) => <span style={{ background: sel ? "#eee" : "" }}>{u.name}</span>}
|
|||
|
|
selectedIds={selected}
|
|||
|
|
onSelect={setId}
|
|||
|
|
/>
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
### HTML 标签聚合组件（Polymorphic）
|
|||
|
|
|
|||
|
|
```tsx
|
|||
|
|
// 基于 JSX.IntrinsicElements 实现 polymorphic component
|
|||
|
|
type PolymorphicComponent<P, D extends keyof JSX.IntrinsicElements> = {
|
|||
|
|
<As extends keyof JSX.IntrinsicElements = D>(
|
|||
|
|
props: P & { as?: As } & JSX.IntrinsicElements[As]
|
|||
|
|
): ReactNode;
|
|||
|
|
};
|
|||
|
|
|
|||
|
|
// Button 可以是 button/div/a 等任何 HTML 元素
|
|||
|
|
const Button: PolymorphicComponent<
|
|||
|
|
{ variant?: "primary" | "secondary" },
|
|||
|
|
"button"
|
|||
|
|
> = ({ variant = "primary", as: Tag = "button", ...props }) => (
|
|||
|
|
<Tag className={`btn btn-${variant}`} {...props} />
|
|||
|
|
);
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
> [!warning] Polymorphic Component 的类型难点
|
|||
|
|
>
|
|||
|
|
> 上述写法是简化版。生产环境通常借助第三方库如 `@radix-ui/react-slot` 来处理复杂的泛型推导，因为要让 `as="a"` 时同时合并 `<a>` 的属性（`href`, `target` 等）而不产生冲突，泛型约束较为复杂。
|
|||
|
|
|
|||
|
|
## Form 校验与 Zod Schema
|
|||
|
|
|
|||
|
|
现代 React + TS 项目中，推荐使用 **Zod** 等 Schema 库将校验逻辑和类型推导合二为一：
|
|||
|
|
|
|||
|
|
```tsx
|
|||
|
|
import { z } from "zod";
|
|||
|
|
|
|||
|
|
// 1. 定义 Schema —— 类型从 schema 自动推导
|
|||
|
|
const LoginSchema = z.object({
|
|||
|
|
email: z.string().email(),
|
|||
|
|
password: z.string().min(8),
|
|||
|
|
});
|
|||
|
|
type LoginFormValue = z.infer<typeof LoginSchema>;
|
|||
|
|
|
|||
|
|
// 2. React Hook Form + ZodResolver 无缝对接
|
|||
|
|
const { register, handleSubmit, formState: { errors } } = useForm<LoginFormValue>({
|
|||
|
|
resolver: zodResolver(LoginSchema),
|
|||
|
|
});
|
|||
|
|
|
|||
|
|
// 3. 模板中使用 —— errors 和 register 都有完整类型提示
|
|||
|
|
<form onSubmit={handleSubmit(onSubmit)}>
|
|||
|
|
<input {...register("email")} placeholder="Email" />
|
|||
|
|
{/* errors.email?.message 有类型提示 */}
|
|||
|
|
{errors.email && <span>{errors.email.message}</span>}
|
|||
|
|
|
|||
|
|
<input {...register("password")} type="password" />
|
|||
|
|
<button type="submit">登录</button>
|
|||
|
|
</form>
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
> [!tip] 为什么选择 Zod 而非 Yup？
|
|||
|
|
>
|
|||
|
|
> - Zod 用 TypeScript 原生语法定义，无需额外 import 类型（Yup 需要 `yupToZooooootTypes` 等桥接方案）
|
|||
|
|
> - Zod 零依赖、性能更优，且支持 `.parse()` 运行时校验与 `.infer()` 类型推导一体化
|
|||
|
|
> - Zod 的错误消息更可定制化
|
|||
|
|
|
|||
|
|
## 常见坑点与避坑指南
|
|||
|
|
|
|||
|
|
> [!failure] 坑1：`any` 的隐式传播
|
|||
|
|
>
|
|||
|
|
> `Array<any>`、`Record<string, any>` 会让整个链条失去类型保护。替代方案：
|
|||
|
|
> - 用 `unknown` 替代顶层 `any`（必须先类型守卫才能使用）
|
|||
|
|
> - 用泛型 `<T>` 传递具体的数据结构
|
|||
|
|
>
|
|||
|
|
> ```tsx
|
|||
|
|
> // ❌ 危险
|
|||
|
|
> const data: Record<string, any> = {};
|
|||
|
|
> data.foo.bar.baz; // 编译通过，运行崩溃
|
|||
|
|
>
|
|||
|
|
> // ✅ 安全
|
|||
|
|
> const data: Record<string, unknown> = {};
|
|||
|
|
> if (typeof data.foo === "object" && data.foo !== null) {
|
|||
|
|
> data.foo.bar; // 需要额外的守卫
|
|||
|
|
> }
|
|||
|
|
> ```
|
|||
|
|
|
|||
|
|
> [!failure] 坑2：事件处理器中的类型收窄失效
|
|||
|
|
>
|
|||
|
|
> 箭头函数无法正确收窄：
|
|||
|
|
> ```tsx
|
|||
|
|
> // ❌ TS 无法推断 e 具体是哪个事件
|
|||
|
|
> <button onClick={(e) => handleClick(e)}>Click</button>
|
|||
|
|
>
|
|||
|
|
> // ✅ 用命名函数保持类型信息
|
|||
|
|
> <button onClick={(e) => handleClick(e)}>Click</button>
|
|||
|
|
> // 但最好直接在属性上写，不包箭头
|
|||
|
|
> <button onClick={handleClick}>Click</button>
|
|||
|
|
> ```
|
|||
|
|
|
|||
|
|
> [!failure] 坑3：useState 初始值的类型陷阱
|
|||
|
|
>
|
|||
|
|
> ```tsx
|
|||
|
|
> // ❌ 类型变成 never[] —— TS 推断了最窄的空数组类型
|
|||
|
|
> const [items, setItems] = useState([]);
|
|||
|
|
> items.push("hello"); // error: Property 'push' does not exist on type 'never[]'
|
|||
|
|
>
|
|||
|
|
> // ✅ 显式声明泛型
|
|||
|
|
> const [items, setItems] = useState<string[]>([]);
|
|||
|
|
>
|
|||
|
|
> // ✅ 或者用 non-empty array 初始化
|
|||
|
|
> const [items, setItems] = useState(["default"]);
|
|||
|
|
> ```
|
|||
|
|
|
|||
|
|
> [!failure] 坑4：React.FC 的副作用
|
|||
|
|
>
|
|||
|
|
> `React.FC` 在早期被广泛推荐，但现在社区趋于弃用原因如下：
|
|||
|
|
> - 它会隐式包含 `children` prop（即使你的组件不需要）
|
|||
|
|
> - 不支持泛型
|
|||
|
|
> - 使得 ReturnType 无法正确推导
|
|||
|
|
> - 使 HOC 的 WrappedComponent 类型丢失
|
|||
|
|
>
|
|||
|
|
> ```tsx
|
|||
|
|
> // ❌ 不推荐
|
|||
|
|
> const MyComponent: React.FC<MyProps> = ({ children }) => <div>{children}</div>;
|
|||
|
|
>
|
|||
|
|
> // ✅ 推荐
|
|||
|
|
> function MyComponent({ children }: MyProps) {
|
|||
|
|
> return <div>{children}</div>;
|
|||
|
|
> }
|
|||
|
|
> ```
|
|||
|
|
|
|||
|
|
## 关联笔记
|
|||
|
|
|
|||
|
|
- [[hhs/REACT/README.md]]
|
|||
|
|
- [[hhs/REACT/1. 基础篇/03-组件与 Props.md]]
|
|||
|
|
- [[hhs/REACT/1. 基础篇/04-State 与不可变性.md]]
|
|||
|
|
- [[hhs/REACT/3. 生态工具篇/08-路由管理.md]]
|
|||
|
|
- [[hhs/REACT/3. 生态工具篇/09-状态管理.md]]
|