changeLocalUserEmail.js

const admin = require("firebase-admin");
const prod = "/prodAccKey.json";
const dev = "/testAccKey.json";

admin.initializeApp({
  credential: admin.credential.cert(require("." + dev)),
});

const auth = admin.auth();
const db = admin.firestore();

function generateTempPassword(length = 8) {
  const chars = "abcdefghjkmnpqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ23456789";
  let password = "";
  for (let i = 0; i < length; i++) {
    password += chars.charAt(Math.floor(Math.random() * chars.length));
  }
  return password;
}

async function changeLocalUserEmail(oldEmail, newEmail) {
  const userRecord = await auth.getUserByEmail(oldEmail);
  const uid = userRecord.uid;
  const tempPassword = generateTempPassword();

  try {
    await auth.updateUser(uid, {
      email: newEmail,
      password: tempPassword,
      emailVerified: true,
    });
  } catch (err) {
    if (err.code === "auth/email-already-exists") {
      console.log(
        `[${new Date().toISOString()}] Cannot update ${uid}: ${newEmail} is already in use by another account`,
      );
      return;
    }
    throw err;
  }
  console.log(
    `[${new Date().toISOString()}] Updated Auth email for ${uid}: ${oldEmail} -> ${newEmail}, Temporary Password: ${tempPassword}`,
  );

  const userDoc = db.collection("User").doc(uid);
  const snapshot = await userDoc.get();
  if (!snapshot.exists) {
    console.log(
      `[${new Date().toISOString()}] No User doc found for ${uid}, skipping Firestore update`,
    );
    return;
  }

  await userDoc.update({ Email: newEmail });
  console.log(
    `[${new Date().toISOString()}] Updated User/${uid} Email field: ${oldEmail} -> ${newEmail}`,
  );
}
//update with the rigtht details
changeLocalUserEmail("old@email.com", "new@email.com").catch(console.error);