Submenu is not displayed on IE11

[lukaszstalmasinski]

• I have searched the issues of this repository and believe that this is not a duplicate.

Reproduction link

https://ant.design/components/menu/#header

Steps to reproduce

1. Go to https://ant.design/components/menu/#header
2. Hover on Navigation Tree - Submenu menu item (Horizontal top navigation menu example)

What is expected?

Submenu should be visible

What is actually happening?

Submenu is not visible

Environment	Info
antd	4.16.6
React	16.13.1
System	Windows 10 1909
Browser	IE11

[github-actions]

Hello @lukaszstalmasinski. We totally like your proposal/feedback, welcome to send us a Pull Request for it. Please send your Pull Request to proper branch (feature branch for the new feature, master for bugfix and other changes), fill the Pull Request Template here, provide changelog/TypeScript/documentation/test cases if needed and make sure CI passed, we will review it soon. We appreciate your effort in advance and looking forward to your contribution!

你好 @lukaszstalmasinski，我们完全同意你的提议/反馈，欢迎直接在此仓库 创建一个 Pull Request 来解决这个问题。请将 Pull Request 发到正确的分支（新特性发到 feature 分支，其他发到 master 分支），务必填写 Pull Request 内的预设模板，提供改动所需相应的 changelog、TypeScript 定义、测试用例、文档等，并确保 CI 通过，我们会尽快进行 Review，提前感谢和期待您的贡献。

[ikonan]

现在依旧还有这个问题， 我这边已经确定 antd:4.15.2 之前都 在ie11 上没有这个bug，之后从4.16.1 开始都会出现二级菜单弹不出的问题。

[hangaoke1]

用了includes方法，antd在编译的时候没有处理，可以自己加个polyfill 或者babel编译的时候把antd加进去

[cwp0]

@afc163 大佬您好，我现在遇到了这个同样的问题，已经尝试过@hangaoke1提出的解决方案，好像没有起作用，请问您还有什么解决办法吗？

[hsluoyz]

用了includes方法，antd在编译的时候没有处理，可以自己加个polyfill 或者babel编译的时候把antd加进去

@hangaoke1 具体思路和代码可以提供下么，也卡在这里了，谢谢~

[yoyo837]

polyfill 就是思路

[afc163]

Try https://stackoverflow.com/questions/57020976/polyfills-in-2019-for-ie11