user.ts

  isAuthenticated() {
    var self = this;
    return new Promise((resolve, reject) => {
      let user = this.cognito.getCurrentUser();
      if (user != null) {
        user.getSession((err, session) => {
          if (err) {
            console.log('rejected session');
            reject()
          } else {
            console.log('accepted session');
            var logins = {};
            var loginKey = 'cognito-idp.' + 
              self.config.get('aws_cognito_region') +
              '.amazonaws.com/' +
              self.config.get('aws_user_pools_id');
            logins[loginKey] = session.getIdToken().getJwtToken();

            AWS.config.credentials = new AWS.CognitoIdentityCredentials({
              'IdentityPoolId': self.config.get('aws_cognito_identity_pool_id'),
              'Logins': logins
            });

            self.user = user;
            resolve()
          } 
        });
      } else {
        reject()
      }
    });
  }