Hhhi

https://www.cnblogs.com/tangshiwei/p/12026915.html https://segmentfault.com/a/1190000014383214 、、

https://blog.csdn.net/cristina_song/article/details/82805444 https://www.codeprj.com/blog/afbc5a1.ht

https://www.jb51.net/article/96083.htm 要彻底理解JS的作用域和Hoisting，只要记住以下三点即可： 1、所有申明都会被提升到作用域的最顶上、、