code: function onSignInConfirmPhoneVerification() {
    var verificationId = $('#signin-phone-verification-id').val();
    var verificationCode = $('#signin-phone-verification-code').val();
    var credential = firebase.auth.PhoneAuthProvider.credential(
        verificationId, verificationCode);
    signInOrLinkCredential(credential);
  }
docs: Confirms a phone number verification for sign-in.