Polyfill not working as expected for IE11

[ChuckJonas]

Bug report

Describe the bug

I keep reading that IE11 is polyfilled "out of the box", however, I'm running into issues where that does not seem to be the case.

The error is NOT coming from a library, but directly from my react component.

TypeError: Object doesn't support property or method 'find'
Anonymous function
./src/pages/profile.tsx:53
  50 | const AccountRoles = (props: { user: User; accounts: Account[] }) => {
  51 |   const { user, accounts } = props;
  52 |   const allRoles = accounts.reduce((roles, acc) => {
> 53 |     const accUser = acc.contactRelations.find(cr => cr.id === user.id);
  54 |     if (!accUser || !accUser.roles) {
  55 |       return roles;
  56 |     }

contactRelations is an array.

To Reproduce

I don't have IE11 but and my app is big and complex so I'm not sure how to create a reproducible example.

1. run find() method on array
2. Open in IE11

Expected behavior

I expect that it should polyfill the find method

System information

• OS: Windows
• Browser: IE 11
• Version of Next.js: 9.2.0

Additional context

I've also tried to polyfill this by following the with-polyfills example, but that doesn't work either. When I try to follow the example, I get an error Module not found: Can't resolve 'core-js/library/fn/object/assign'

[Timer]

Please try next@canary.

[ChuckJonas]

I don't have a window machine, and the dev who found the bug is out for the day.

Will try first thing tomorrow.

FYI: I got the polyfill example to work. For some reason I had to put the entry changes at the bottom of my next.config.js, even though I wasn't modifying entry in any other way.

[ChuckJonas]

I was able to figure out how to test. Looks like upgrading did fix the issue

[balazsorban44]

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