Depdency injection OOP vs FP in javascript. A use case for currying. Partial application.

fp-oop-di.js

// -----------------------------------------------
// OOP dependency injection (the repository implementation can be switched in runtime)
// -----------------------------------------------
class UserService {
  constructor(userRepository) {
    this.userRepository = userRepository
  }

  create(params) {
    validate(params)
    return this.userRepository.create(params)
  }
}

const mysqlUserRepository = MysqlUserRepository.build(...)
const mongoDbUserRepository = MongoDbUserRepository.build(...)

const mysqlUserService = new UserService(mysqlUserRepository)
const user = mysqlUserService.create({name: 'Carlos'})

const mongoDbUserService = new UserService(mongoDbUserRepository)
const anotherUser = mongoDbUserService.create({name: 'Pedro'})

// ---------------------------------------------
// FP dependencies with currying v1 
// (the function in charge of persistence can be switched in runtime)
// ---------------------------------------------

function createUser(params) {
  validate(params)
  return function(persistFn) {
    return persistFn(params)
  }
}

function persistUserMysql(params) { ... }
function persistUserMongoDb(params) { ... }

const user = createUser({name: 'Carlos'})(persistUserMysql)

const anotherUser = createUser({name: 'Pedro'})(persistUserMongoDb)