ES6 模块化 export 和import

1.定义模块：

export const a = 1
export default b = 2

2.导入模块

import {a} from './xxxxx'
import b from './xxxxx'

3.区分什么时候import 需要花括号，什么时候不需要

当使用export default 导出的模块，导入的时候就不需要花括号，否则都需要花括号

4.导出另命名

 const a =1
 const b = 2
export {a as apple,b as bananer}

导入接收

import {apple,bananer} from './xxx'

5.导入另命名

const a =1
 const b = 2
export {a,b}

导入

import {a as apple,b as bananer} from './xxx'
console.log(apple,bananer)

6.导入全部

import * as newModule from './xxx'
console.log(newModule)