DHIS2 web app working offline

We are developing a custom web app which creates/updates tracked entities and events. We have some custom actions that’s why we are not directly using tracker entry form inside DHIS2.

As the web app can only communicate with DHIS2 via API, the app does not work when internet is not available. Now the client has considered that as ‘inability of the vendor’ to implement offline web app!! According to client - DHIS2 works offline, so the app should also.

Does the web app allow ‘caching data in a local db’? Or any workaround possible to use web app in online/offline mode?

@austin any help?