const clientId = 'YOUR_AUTH0_APPLICATION_CLIENT_ID';
const domain = 'YOUR_AUTH0_APPLICATION_DOMAIN';

const auth = new auth0.Authentication({
doamin,
clientID: clientId,
scope: 'openid profile email',
responseType: 'code'
});

// mfaDefaultOptions
// Auth0MFAFLow default config is for oob type with just sms channel
// see https://auth0.com/docs/api/authentication#multi-factor-authentication
// for more details and otp type
const options = {
challengeType: 'oob', // or 'otp'
oobChannels: ['sms'],
authenticatorTypes: ['oob'], // or ['otp']
grantType: 'http://auth0.com/oauth/grant-type/mfa-oob'
};

const mfaAuth = new Auth0MFAFLow(clientId, domain); // add options as a 3rd parameter

const startMultiFactorAuth = (mfaToken) => {
// SHOW MOBILE NUMBER INPUT FIELD
const mobileNumber = 'GET_THE_USER_MOBILE_NUMBER'; // OPTIONAL for oob ( Required if sms or voice )
// get the mobile number from the user if required
const {error} = mfaAuth.start(mfaToken, mobileNumber);
if (!error) {
// SHOW OTP INPUT FIELD
// to resend the OTP call mfaAuth.challenge()
// once user enters OTP and submits form, call onOtpSubmit
} else {
// SHOW ERROR MESSAGE
}
};

const onOtpSubmit = async (otp) => {
const {data} = await mfaAuth.complete(otp);
if (data) {
// data contains your access_token
auth.userInfo(data.access_token, async (error, profile) => {

});
} else {
// SHOW ERROR MESSAGE
}
};