verify-sms-code-express.js

import { google } from 'googleapis';

app.post('/sendSMS', function (req, res) {
  const { phoneNumber, recaptchaToken } = req.body;
  
  const identityToolkit = google.identitytoolkit({
    auth: 'GCP_API_KEY',
    version: 'v3',
  });
  
  await identityToolkit.relyingparty.verifyPhoneNumber({
        code: verificationCode,
        sessionInfo: phoneSessionId,
      });
  
 // verification code accepted, update phoneNumberVerified flag in database
 // ...
});

i believe there is a small issue with that code phoneSessionId is unidentified

import { google } from 'googleapis';

app.post('/sendSMS', function (req, res) {
  const { phoneNumber, recaptchaToken } = req.body;
  
  const identityToolkit = google.identitytoolkit({
    auth: 'GCP_API_KEY',
    version: 'v3',
  });
  
  const response = await identityToolkit.relyingparty.sendVerificationCode({
    phoneNumber,
    recaptchaToken: recaptcha,
  });
  
 // save sessionInfo into db. You will need this to verify the SMS code
 const sessionInfo = response.data.sessionInfo;
 
});