TypeScript在React项目中的使用实践总结

const MyComp: React.FC<{ title: string; }> = ({title}) => <h2>{title}</h2>;

// ReactNode
const a: React.ReactNode =
  null ||
  undefined || <div>hello</div> || <MyComp title="world" /> ||
  "abc" ||
  123 ||
  true;

// ReactElement和JSX.Element
const b: React.ReactElement = <div>hello world</div> || <MyComp title="Good" />;

const c: JSX.Element = <MyComp title="good" /> || <div>hello world</div>;

// input输入框输入文字
const handleInputChange = (evt: React.ChangeEvent<HTMLInputElement>) => {
  console.log(evt);
};

// button按钮点击
const handleButtonClick = (evt: React.MouseEvent<HTMLButtonElement>) => {
  console.log(evt);
};

// 移动端触摸div
const handleDivTouch = (evt: React.TouchEvent<HTMLDivElement>) => {
  console.log(evt);
};

// ❌这样写是不必要的，因为初始值0已经能说明count类型
const [count, setCount] = useState<number>(0);

// ✅这样写好点
const [count, setCount] = useState(0);

interface IUser {
  name: string;
  age: number;
}

const [user, setUser] = React.useState<IUser | null>(null);

console.log(user?.name);

// 连接DOM，初始值赋值为null，不能是undefined，如要指明泛型变量需要具体到HTMLxxxElement
// 如果我们确定inputRef.current在调用时一定是有值的，可以使用非空断言，在null后添加!
const inputRef = useRef<HTMLInputElement>(null!);

const handleClick = () => {
  inputRef.current.focus(); // 当然不用非空断言，用inputEl.current?.focus()可选链也是可以的
}

return (
  <input ref={inputRef} />
  <button onClick={handleClick}>点击</button>
)

// 通过初始值来自动指明泛型变量类型
const sum = useRef(0);

// 通过.current直接赋值
sum.current = 3;
// 不存在异步更新问题
console.log(sum.current); // 3

const store = createStore(rootReducer);

export type RootState = ReturnType<typeof rootReducer>;

const { var1, var2 } = useSelector((store: RootState) => store.xxx);

const useInfo = () => {
  const [age, setAge] = useState(0);

  return [age, setAge] as const; // 类型为一个元组，[number, React.Dispatch<React.SetStateAction<number>>]
};

import { AnyAction } from "redux";

const DEF_STATE = {
  count: 0,
  type: 'integer'
};

// 使用redux的AnyAction放宽限制
function countReducer(state = DEF_STATE, action: AnyAction) {
  switch (action.type) {
    case "INCREASE_COUNT":
      return {
        ...state,
        count: state.count + 1,
      };
    case "DECREASE_COUNT":
      return {
        ...state,
        count: state.count - 1,
      };
    default:
      return state;
  }
}

export default countReducer;

// 比如当前组件名为InfoCard
export interface InfoCardProps {
  name: string;
  age: number;
}

export interface GetUserInfoReqParams {
    
    name: string;
    
    age: number;
    
    gender: string;
}

// 表示键名不确定，键值限制为number类型
export interface NotSureAbouTKEy {
  [key: string]: number;
}

// 当键名键值都不确定时，以下接口对任何对象都是适用的
export interface AllNotSure {
  [key: string]: any;
}

// 通常，我们会为接口的泛型变量指定一个默认类型
interface IHuman<T = unknown> {
  name: string;
  age: number;
  gender: T;
}

// 其他地方使用时
const youngMan: IHuman<string> = {
    name: 'zhangsan',
    age: 18,
    gender: 'male'
}