Polyfill Demo not working in IE11

[JSMike]

SCRIPT1002: Syntax error
dialog-polyfill (159,58)

SCRIPT5007: Unable to get property 'toString' of undefined or null reference
dialog-polyfill (117,3)

This is referring to issues in the html file for the demo site, not the library.

dialog-polyfill/index.html

Line 159 in 5033aac

const button = createButton('Show', options.modal ? () => dialog.showModal() : () => dialog.show());

IE11 doesn't support arrow functions https://caniuse.com/?search=arrow%20function

dialog-polyfill/index.html

Line 117 in 5033aac

errorNode.textContent = event.error.toString();

event.error is undefined

[JSMike]

error.message exists in ie11.

errorNode.textContent = event.error ? event.error.toString() : event.message;