They shouldn’t know anything about your back-end web service.
Sounds like you are talking about making a hybird app though, which is also fine (and is technically a client). There are a ton of hybrid frameworks out there: Ionic, Cordova, Cocoon, PhoneGap, apparently Trigger.io, etc. They wouldn’t be useful if app stores rejected them.
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solved will the app store reject my app if I use a javascript sdk for the backend? [closed]