Uncaught SyntaxError: Unexpected token import

报错代码：

 import Vue from 'vue'
import App from './App.vue'
import yun from 'yun-ui'
import 'yun-ui/dist/yun/index.css'
import {Button} from 'yun-ui'
import 'yun-ui/dist/yun/Button/index.css'

https://segmentfault.com/q/1010000005130270/a-1020000005130833

https://stackoverflow.com/questions/42185035/webpack-uncaught-syntaxerror-unexpected-token-import