Arrow functions cause issues on IE

[ChristophWurst]

Similar to fixes like #12340 and #12860, we have to make sure our scripts and script bundles don't use the arrow function syntax as it's not supported on IE.

Steps to reproduce

1. Use arrow function in a script
2. Transpile with babel
3. Still get a syntax error

Expected behaviour

Scripts should work on all supported browsers, including IE. Apps (and server) should use the transformation plugin for Babel like nextcloud-libraries/nextcloud-password-confirmation#2.

Actual behaviour

Sytax errors and therefore broken scripts.

Server configuration

Nextcloud version:

Starting somewhere around Nextcloud 14

---

• Update notification
  • https://github.com/nextcloud/server/blob/v14.0.3/apps/updatenotification/js/updatenotification.js#L26
• Settings

... not a complete list yet, needs investigation

cc @nextcloud/javascript

[juliusknorr]

Seems fixed to me with 15dc9d8 for updatenotifications and settings has a proper babelrc file as well.