Is there any sense to useContext in React? - reactjs

Question

Hello i need help with my app.
What sense is to put my User data to useContext if when i refresh page all data disapear?
How to make this context permament?
I have been sitting with this all day, and when i try to get data in HomePage, everything is ok until i refresh page.
The second question is about JWT. It's used only on server side, right? It's verifing the token when I'm making server reqest only?
below is my code
App.js
import Navbar from "./components/Navbar";
import AddNewAnnoucement from "./components/pages/AddNewAnnoucement/AddNewAnnoucement";
import { Route, Routes } from 'react-router-dom';
import Home from "./components/pages/Home";
import Annoucements from "./components/pages/Annoucements/Annoucements";
import Register from "./components/pages/Register/Register";
import Login from "./components/pages/Login/Login";
import { useState, useMemo, useEffect, createContext } from "react";
import { getProfile, tokenIsValid } from './service/userService.js'
export const UserContext = createContext();
function App() {
const [userData, setUserData] = useState({
token: undefined,
user: undefined,
})
useEffect(() => {
const isLoggedIn = async () => {
let token = localStorage.getItem("token")
if (token == null) {
localStorage.setItem("token", "")
token = ""
}
const tokenResponse = tokenIsValid(token);
tokenResponse.then((res) => {
if (res.data) {
const userResponse = getProfile(token);
userResponse.then((res) => {
setUserData({
token: token,
data: res.data
})
})
}
}).catch((err) => {
console.log(err);
}
)
}
isLoggedIn();
}, [])
return <>
<UserContext.Provider value={{ userData, setUserData }}>
<Navbar />
<div className='container'>
<Routes>
<Route path='/' element={<Home />} />
<Route path='/annoucements' element={<Annoucements />} />
<Route path='/annoucements/add' element={<AddNewAnnoucement />} />
<Route path='/register' element={<Register />} />
<Route path='/login' element={<Login />} />
</Routes>
</div>
</UserContext.Provider>
</>
}
export default App;