Firebase Detecting if user exists

Question

How Can I Check user exists in Firebase auth in Signup Button via react native?

This is my Login Page Code:

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Answer 1

You need to use the fetchSignInMethodsForEmail API. It takes an email and returns a promise that resolves with the list of providers linked to that email if it is already registered: https://firebase.google.com/docs/reference/js/firebase.auth.Auth.html#fetchsigninmethodsforemail