transaction-example.js

let transaction
let teamToUpdate
try {
  transaction = await sequelize.transaction() // Managed Transaction
  
  // update the team
  teamToUpdate = await Team.findOne({ where: {...}, transaction })
  /* POTENTIAL ERROR - .update of null */
  await teamToUpdate.update({...}, {transaction})
  
  // Associate the team to Tags
  let tagModels = []
  for (let i = 0; i < teamProperties.tags.length; i++) {
    /* CUSTOM ERROR no tag */
    let tag = await Tag.findById(teamProperties.tags[i], {transaction})
    if (!tag) throw new Error('tag not found')
    tagModels.push(tag)
  }
  await teamToUpdate.setTags(tagModels, {transaction})
  
  // everything worked as planned - commit the changes
  await transaction.commit()
} catch (err) {
  // we'll write this after
}