Làm thử React condition rendering | Hướng dẫn học React.js

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<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <title>Hello React</title>
    <script src="https://unpkg.com/react@16/umd/react.development.js"></script>
    <script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
    <script src="https://unpkg.com/@babel/standalone/babel.min.js"></script>
  </head>
  <body>
    <div id="root"></div>

handleLoginClick = () => {
          this.setState({isLoggedIn: true});
        };

handleLogoutClick = () => {
          this.setState({isLoggedIn: false});
        };

render() {
          const isLoggedIn = this.state.isLoggedIn;
          let button; /* Khai báo biến button sử dụng cho if */

if (isLoggedIn) {
            button = <LogoutButton onClick={this.handleLogoutClick} />;
          } else {
            button = <LoginButton onClick={this.handleLoginClick} />;
          }

return (
            <div>
              <Greeting isLoggedIn={isLoggedIn} />
              {button}
            </div>
          );
        };
      };

const UserGreeting = (props) => {
        return <h2>Welcome back!</h2>;
      };

const GuestGreeting = (props) => {
        return <h2>Please sign up.</h2>;
      };

const Greeting = (props) => {
        const isLoggedIn = props.isLoggedIn;
        if (isLoggedIn) {
          return <UserGreeting />;
        }
        return <GuestGreeting />;
      };

const LoginButton = (props) => {
        return (
          <button onClick={props.onClick}>
            Login
          </button>
        );
      };

const LogoutButton = (props) => {
        return (
          <button onClick={props.onClick}>
            Logout
          </button>
        );
      };

ReactDOM.render(
        <LoginControl />,
        document.getElementById('root')
      );
    </script>
  </body>
</html>

React render có điều kiện