The app on iOS or android would make the frontend whereas the the API or the code for interacting with the database, and receiving and sending data to and from the app is called the backend. Now React Native is responsible only for the front end, i.e. the app, part of the whole application .
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React (JavaScript library) Original author(s)Jordan WalkeWritten inJavaScriptPlatformWeb platformTypeJavaScript libraryLicenseMIT LicenseReact (JavaScript library) – Wikipedia en.wikipedia.org › wiki › React_(JavaScript_library)
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