react条件渲染完整代码

以下是React条件渲染的完整代码示例：

import React from 'react';

class App extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      isLoggedIn: false
    };
  }

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

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

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

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

function UserGreeting(props) {
  return <h1>Welcome back!</h1>;
}

function GuestGreeting(props) {
  return <h1>Please sign up.</h1>;
}

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

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

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

export default App;