Sequelize Transaction sample

sequelize_transaction_sample.js

 const t = await db.sequelize.transaction();
                        const promises = [];
                        for (let i = 0; i < usersData.length; i++) {
                            promises[i] = UserRepository.createUser(usersData[i], {transaction: t});
                        }
                        Promise.all(promises).then(users => {
                            const userRolePromises = [];
                            for (let i = 0; i < users.length; i++) {
                                userRolePromises.push(RoleRepository.findRoleById(rows[users[i].email]).then(role => {
                                    users[i].addRole(role);
                                    return users[i];
                                }));
                            }
                            return Promise.all(userRolePromises);
                        }).then(function (users) {
                            let emailPromises = [];

                            users.forEach(user => {
                                const email = user.email;
                                const verification_hash = user.verification_hash;
                                const registrationLink = registrationLinkPrefix + '/' + verification_hash;
                                const {subject, text} = buildVerificationEmail(email, registrationLink);
                                emailPromises.push(sendEmail(email, subject, text, res));
                            });

                            return Promise.all(emailPromises);
                        }).then((result) => {
                            t.commit();
                            res.send(result);
                        }).catch(function (err) {
                            t.rollback();
                            console.log(err);
                            // t.rollback();
                            return res.status(400).json({error: err.toString});
                            // res.status(400).json({ message: errMessage });
                        });