React.js中内容显示组件的呈现中的条件

render() {
  if (this.state.isLoggedIn) {
    return <div>Welcome, User!</div>;
  } else {
    return <div>Please log in.</div>;
  }
}

render() {
  return (
    <div>
      {this.state.isLoggedIn ? <div>Welcome, User!</div> : <div>Please log in.</div>}
    </div>
  );
}

render() {
  return (
    <div>
      {this.state.isLoggedIn && <div>Welcome, User!</div>}
    </div>
  );
}