$rootScope replacement in ionic5

what we use instead of $rootScope in ionic5/typescript.

Mutually injected service providers.

@rapropos please suggest any doc or video reference,i am new in typescript/ionic4.
any clue for connecting loopback4 api with ionic4 also suggest

Tour of Heroes, especially chapter 4 on services.

@rapropos thanks a lot man ,your suggestion is really helpful.

@rapropos now i want your more support towards loopback4 apis and ionic5 application connection.