containers/App/index.js

Now, let's create some of the user interfaces. We'll start by creating our main container—app. So, inside app/index.js, you'll see the following code:

const AppWrapper = styled.div`
  max-width: calc(768px + 16px * 2);
  margin: 0 auto;
  display: flex;
  min-height: 100%;
  padding: 0 16px;
  flex-direction: column;
  .btn {
    line-height: 0;
  }
`;

// eslint-disable-next-line
class App extends Component {
  render() {
    return (
      <AppWrapper>
        <Header />
        <Switch>
          <Route exact path="/" component={HomePage} />
          <Route exact path="/login" component={LoginPage} />
          <Route exact path="/register" component={RegisterPage} />
          <Route exact path="/about" component={AboutPage} />
          <Route exact path="/contact" component={ContactPage} />
          <Route path="" component={NotFoundPage} />
        </Switch>
        <Footer />
       </AppWrapper...