install react-router-dom
then create two components one for valid users and other for invalid users.
try this on app.js
import React from 'react';
import {
BrowserRouter as Router,
Route,
Link,
Switch,
Redirect
} from 'react-router-dom';
import ValidUser from "./pages/validUser/validUser";
import InValidUser from "./pages/invalidUser/invalidUser";
const loggedin = false;
class App extends React.Component {
render() {
return (
<Router>
<div>
<Route exact path="/" render={() =>(
loggedin ? ( <Route component={ValidUser} />)
: (<Route component={InValidUser} />)
)} />
</div>
</Router>
)
}
}
export default App;