一、跨层级传递
import { useContext, createContext, useState } from "react"const msgContext = createContext()
function A(){const m = useContext(msgContext)return (<div>A-{m}<B></B></div>
)
}
function B(){const m = useContext(msgContext)return (<div>B-{m}</div>
)
}function App(){const message = 'my name is msg'return (<div><msgContext.Provider value={message}><A ></A></msgContext.Provider> </div>
)
}export default App