Simple example of procedural approach to clean architecture without interfaces

procedural.ts

import * as z from 'zod';

// ENTITY ========================================================

const userEntityPresenter = z.object({
  id: z.number(),
  name: z.string(),
  email: z.string()
});

type UserEntity = z.infer<typeof userEntityPresenter>;

// DTOS ========================================================

const createUserInput = z.object({
  name: z.string().max(255),
  email: z.string().email().max(255)
})

type UserCreationDTO = z.infer<typeof createUserInput>;


// REPOSITORY ========================================================

class UserRepository {
  createUser (input: UserCreationDTO): UserEntity {
    return {
      id: 1,
      ...input
    }
  }
}

// Base case =========================================================

abstract class Case {
  constructor() {
    this.execute = this.execute.bind(this);
  }
  abstract execute(input: unknown): unknown;
}

// Case ==============================================================

type Dependency = {
  userRepository: UserRepository;
}

class CreateUserCase extends Case {
  readonly payload = createUserInput;
  readonly presenter = userEntityPresenter;

  constructor(readonly dependencies: Dependency) {
    super();
  }

  /**
   * @throws {z.ZodIssue} - If the input is invalid
   */
  async execute (input: UserCreationDTO): Promise<UserEntity> {
    const values = this.payload.parse(input);
    const user = this.dependencies.userRepository.createUser(values);
    return this.presenter.parse(user);
  }
}

const userRepository = new UserRepository();
export const createUser = new CreateUserCase({userRepository}).execute;

// EXPRESS CONTROLLER ================================================

export function createUserController (req, res, next) {
  const user = createUser(req.body);
  res.json(user);
}