expires-at.js

handleAuthentication() {
  return new Promise((resolve, reject) => {
    this.auth0.parseHash((err, authResult) => {
      if (err) return reject(err);
      if (!authResult || !authResult.idToken) {
        return reject(err);
      }
      this.idToken = authResult.idToken;
      this.profile = authResult.idTokenPayload;
      // set the time that the id token will expire at
      this.expiresAt = authResult.idTokenPayload.exp * 1000;
      resolve();
    });
  })
}

Cracking, that makes more sense, thank you