React CRUD App.

1. Routes in react js. (react-router-dom)
   
   
2. Avoid page reloading here if you clicked on other options (Home, About, Contact)
1. Use <Link> Component instead of  `a` tag
2. To change the active tabs use <NavLink> instead of <Link> and use `exact ` attribue.
1. <NavLink className="nav-link" exact to="/">Home</NavLink>
   
   
3. 404 Page
1. <Route component={Notfound} />
   
   
4. Fake Json Server. 
1. npm i json-server
2. Create db.json file with dummy data from JSON placeholder.
   
   
5. Run Server & React with single npm install
1. Run 2 scripts at once. ( concurrently )
   
   
6. Async functions
   
   
7. In React if you want to use variables from .env you must use the `REACT_APP_` prefix Like this `REACT_APP_DB_SERVER_URL`.
1. And you must restart the server.
   
   
8. useHistoy Hook.
   
   
9. Edit particular user in react.
1. http://localhost:3000/users/edit/1
2. You can use `useParams` Hooks to get values from the URL.