//mod1.js
export let a = 12
//默认成员
export default xxx
引入模块
//index.js
//引入全部
import * as mod1 from './mod1'
//引入default成员
import mod1 from 'xxx'
import {a,b as name2} from 'xxx'
//只引入
import 'xxx'
//异步引入
let p = import('./mod1')
console.log(mod1.a)// 12