How to add custom (angular) function?

I am extending admin keycloak and want to add custom split string (to array) function …

I try to register this with module.filter, with the module build on angular.module…

However angular is not recognised…
I add a own custom .js file in the resource folder and referenced it in the theme.properties.
The folder build up is correct since it does recognise my code and css etc is working.

Is this even possible or is there another way…

What i want is an ng-repeat that splits a string that is seperates by a “,”…