1.学习{props.children}的用法

function ChildComponent(props){
  return (
    <div>
  {props.children}
  </div>
  );
}

function ParentComponent() {
  return (
    <ChildComponent>
      <h1>abcd</h1>
      <h2>efgh</h2>
    </ChildComponent>
   
  );
}

ReactDOM.render(
  <ParentComponent />,
  document.getElementById('root')
);