IE11 polyfills don't work for React app. Why?

Question

In IE11 I get these errors:

But i have react-app-polyfill installed and imported in index.js first line:

Answer 1

You also need to add ie 11 in package.json like this: 

For more information, you can refer to this answer. I create a new React app according to this then do the steps in the answer I mention above, the React app can work well in IE 11.