This week we encountered a bug on Izime that was only reproducible on iOS 11, to be more specific 11.0. The issue wasn't reproducible on iOS 11.4. The bug was traced to this line.
const notifications = data?.pages.flat();
We wrongly assumed Babel would transform to a compatible implementation for older iOS versions. A good pointer is to check the React Native documentation when you want to use new syntax.
One option was to use the oldschool implementation:
const notifications = .concat(...data?.pages);
Or the very oldschool implementation:
const notifications = .concat.apply(, data?.pages);
But eventually we decided on adding a polyfill ourselves. So we can keep on using the hip syntax without any issues.