Create Sequelize Model Facebook DataLoader

createModelLoader.js

const _ = require('lodash')
const { Op } = require('sequelize')
const DataLoader = require('dataloader')

// eslint-disable-next-line
const createModelLoader = (Model, inField) => {
  return new DataLoader(async (keys) => {
    // Create id:index map for further use
    const idIndexMap = keys.reduce((map, key, index) => {
      map[key] = index
      return map
    }, {})

    // Query all models in keys
    const models = await Model.findAll({
      where: { [inField]: { [Op.in]: keys } }
    })

    // create empty array size match keys size
    const result = Array.from(keys).fill(undefined)

    // map user to match key index
    _.forEach(models, (model) => {
      const index = idIndexMap[model[inField]]
      result[index] = model
    })

    return result
  })
}


module.exports = {
  createModelLoader
}