asb_cloud_front/src/App.js

import './styles/App.less'
import React /*, { useContext, createContext, useState }*/ from "react"
import {
  BrowserRouter as Router,
  Switch,
  Route,
  Redirect
} from "react-router-dom"
import Login from './pages/Login'
import Main from './pages/Main'
import {OpenAPI} from './services/api'

OpenAPI.BASE = 'http://localhost:3000'
OpenAPI.TOKEN = localStorage['token']

function PrivateRoute({ children, ...rest }) {  
  let token = localStorage['token']
  return (
    <Route
      {...rest}
      render={({ location }) =>
        token 
        ? (children) 
        : (<Redirect to={{pathname: "/login", state: { from: location }}}/>)
      }
    />
  );
}

export default function App() {
  return (
    <Router>
        <Switch>
          <Route path="/login">
            <Login />
          </Route>
          <PrivateRoute path="/">
            <Main />
          </PrivateRoute>
        </Switch>
    </Router>
  )
}