How to fix auth/email-already-in-use in Firebase

import { createUserWithEmailAndPassword } from 'firebase/auth';

createuserWithEmailAndPassword(auth, email, password)
  .then((userCredential) => {
    console.log('User created:', userCredential.user);
  })
  .catch((error) => {
    if (error.code === 'auth/email-already-in-use') {
      console.log('Email already in use!');
    }
  });

if (error.code === 'auth/email-already-in-use') {
  setErrorMessage('This email is already registered. Please sign in instead.');
  // Optionally show a button to redirect to login page
}

import { fetchSignInMethodsForEmail } from 'firebase/auth';

async function handleSignUp(email, password) {
  try {
    const methods = await fetchSignInMethodsForEmail(auth, email);
    
    if (methods.length > 0) {
      setErrorMessage('This email is already registered.');
      return;
    }
    
    // Safe to proceed with account creation
    await createUserWithEmailAndPassword(auth, email, password);
  } catch (error) {
    console.error('Sign-up error:', error.message);
  }
}

if (error.code === 'auth/email-already-in-use') {
  return (
    <div>
      <p>This email is already registered.</p>
      <button onClick={() => navigateTo('/login')}>Sign In</button>
      <p>or try signing up with a different email</p>
    </div>
  );
}

if (error.code === 'auth/email-already-in-use') {
  // User can sign in with the existing method (e.g., Google)
  setErrorMessage(
    'This email is already associated with another sign-in method. Please sign in with that method.'
  );
}