ES6 import/export

export {default} from './Header.js';
<!--等价于-->
import Header from './Header.js';
export Header;

export {default as Header, HeaderAction } from './Header.js';
<!--等价于-->
import Header, { HeaderAction } from './Header.js';
export Header;
export HeaderAction;

// 导出除默认变量以外的所有变量
export {*} from './Header.js';
// 导出默认变量
export {default} from './Header.js'