// ...
const getModule = (config) => {
  const documentClient = new AWS.DynamoDB.DocumentClient(config)

  return ({
    // ...
    flatUpdateParams: params => ({
      UpdateExpression: `set ${Object.entries(params)
        .map(([key]) => `#${key} = :${key}, `)
        .reduce((acc, str) => acc + str)
        .slice(0, -2)}`,
      ExpressionAttributeNames: Object.keys(params).reduce(
        (acc, key) => ({
          ...acc,
          [`#${key}`]: key
        }),
        {}
      ),
      ExpressionAttributeValues: Object.entries(params).reduce(
        (acc, [key, value]) => ({
          ...acc,
          [`:${key}`]: value
        }),
        {}
      )
    })
  })
}
// ...