Why useEffect gets executed before child compenents rendered?

i have unexpected behaviour. "user" variable that i declared at the top of App compenent is null by default.

At the first start or refresh of path=/, useEffect of App compenent gets executed before child compenent which is Login, What is the reason of this behaviour ?

App.js

import { BrowserRouter, Routes, Route, Navigate } from 'react-router-dom'
import { useAuthContext } from './hooks/useAuthContext'
import { useEffect }from 'react'
// pages & components
import Home from './pages/Home'
import Login from './pages/Login'
import Signup from './pages/Signup'
import Navbar from './components/Navbar'
function App() {
const { user } = useAuthContext()
useEffect(() => {
console.log("App useffect")
}, [])
return (
<div className="App">
<BrowserRouter>
<Navbar />
<div className="pages">
{console.log("Route main")}
<Routes>
<Route 
path="/"
element={user ? <Home /> : <Navigate to="/login" /> } 
/>
<Route 
path="/login" 
element={!user ? <Login /> : <Navigate to="/" />} 
/>
<Route 
path="/signup" 
element={!user ? <Signup /> : <Navigate to="/" />} 
/>
</Routes>
</div>
</BrowserRouter>
</div>
);
}
export default App;

Login.js

import { useEffect }from 'react'
const Login = () => {
console.log('Login here:')
useEffect(() => {
console.log("Login here:' useffect")
}, [])
return (
<div>Login</div>
)
}
export default Login

Navigate is a React component. According to documentation: "A <Navigate> element changes the current location when it is rendered.".

It means that your App.js is getting rendered and it renders the Navigate component first as you hit / route and then your App.js useEffect trigger. After <Navigate> component changes the location to /login- your Login.js is getting rendered by the react router and then useEffect in Login.js trigger.

This is what <Navigate /> simply looks like,

function Navigate() {
React.useEffect(
() => navigate(JSON.parse(jsonPath), { replace, state, relative }),
[navigate, jsonPath, relative, replace, state]
);
return null;
}

It also uses a useEffect to handle the side-effect ( replace the url ) and the render phase of the <Navigate /> returns just null.

So it works as expected. It renders your App, then It renders your <Navigate /> which returns null. Rendering completed and then it executed the side effects. Then after all of that, the side effect in the <Navigate /> is the one which causes to render <Login /> page.