A bulkUpsert function using Promises and the Sequelize API

sequelize-bulk-upsert.js

module.exports = function bulkUpsert(model, key, values) {
  function _find(where) {
    return model.findOne({ where })
  }

  function _update(value, where) {
    return model
      .update(value, { where })
      .then(() => _find(where))
  }

  let promises =
    values.map(value => {
      let where = { 
        [key]: value[key]
      }

      return model
        .findOrCreate({ where, defaults: value })
        .spread((result, created) => {
          return (!created) 
            ? _update(value, where) 
            : Promise.resolve(result)
        })
    })

  return Promise.all(promises)
}