javascript导出语法之间有什么区别？

Question

我试图了解在javascript中导出组件的方式之间是否存在任何差异。我了解默认导出的工作方式，以及如何导出变量，例如：

// when exporting a function:
export function foo () {}
// you can import it as
import {foo} from "foo";

// default export
export default class foo {}
//then:
import foo from "foo";

但是我见过类似的情况：

export {foo as default} from "foo";
export {foo as default, bar} from "foo";
export {default} from "foo";
export {default as foo} from "foo";

有人可以解释在上述4种情况下default关键字的含义，以及如何导入它？

Answer 1

// import foo and export it as default
export {foo as default} from "foo"; 

// import foo and export it as default
// import bar and immediately export bar
export {foo as default, bar} from "foo";

// import default as foo and export it
export {default as foo} from "foo"; 

// re-exporting the default export 
export {default} from "foo";

所有这些都是转口产品，意思是进口并立即出口。