react 结合 ts

useState 中使用 ts

type User = {
    name: string
    age: number
}
function App() {
    // 直接使用对象
    // const [user, setUser] = useState<User | null>(null)
    // const [user, setUser] = useState<User>({
    //     name: 'jack',
    //     age: 18
    // })
    // 使用函数返回对象
    const [user, setUser] = useState<User>(()=> {
        return {
            name: 'jack',
            age: 18
        }
    })
    // setUser 也同理有 直接修改 和 使用函数返回对象 的修改形式
    return (
        <>this is an app</>
    )
}
export default App

props 中使用 ts

type Props = {
    className: string
    children: React.ReactNode
}
function Button(props: Props) {
    const {className, children} = props
    return <button className={className}>{children}</button>
}

type Props = {
    onGetMsg?: (msg: string) => void
}
function Button(props: Props) {
    const {onGetMsg} = props
    const clickHandler = () => {
        onGetMsg?.('hello')
    }
    return <button onClick={clickHandler}>sendMsg</button>
}
function App() {
    return (
        <>
            {/*内联函数会自动进行类型推导，如果是外部函数 还需要手动进行类型约束*/}
            <Button onGetMsg={(msg) => console.log(msg)}/>
        </>
    )
}
export default App

useRef 使用 ts

function App() {
    const domRef = useRef<HTMLInputElement>(null)
    useEffect(() => {
        console.log(domRef.current?.value)
    }, []);
    return (
        <>
            <input ref={domRef}/>
        </>
    )
}
export default App

function App() {
    const timerRef = useRef<number | undefined>(undefined)
    useEffect(() => {
        timerRef.current = setInterval(() => {
            console.log('1')
        }, 1000)
        return ()=> clearInterval(timerRef.current)
    }, []);
    return (
        <>this is div</>
    )
}