官方指引：

https://developer.mozilla.org/en-US/docs/web/javascript/reference/statements/import

https://developer.mozilla.org/en/docs/web/javascript/reference/statements/export

require和import的区别 ？

参考：https://www.zhihu.com/question/56820346

参考：https://www.cnblogs.com/guanghe/p/6560698.html