mkdir modular-system
cd modular-system
npm init -y

npm install express mongoose zod
npm install -D typescript @types/node @types/express ts-node-dev

ts --init

{
  "compilerOptions": {
    "target": "ES6",
    "module": "commonjs",
    "outDir": "./dist",
    "rootDir": "./src",
    "strict": true,
    "esModuleInterop": true
  }
}

src/
 |-- modules/
 |    |-- user/
           |-- user.interface.ts       // make an TS interface/type for specific model
 |         |-- user.model.ts           // create schema from type and then make a model 
 |         |-- user.controller.ts      // handle req/res only
 |         |-- user.service.ts         // habdle business logic or query
 |         |-- user.zod.validation.ts  // third party extension to handle validation
 |         |-- user.router.ts          // make route and connect it into userController.
 |-- app.ts
 |-- server.ts

import { Schema, model } from 'mongoose';

// we can make it into different file as name user.interface.ts 
interface IUser {
  name: string;
  email: string;
  password: string;
}
const userSchema = new Schema<IUser>({
  name: { type: String, required: true },
  email: { type: String, required: true, unique: true },
  password: { type: String, required: true },
});

export const User = model<IUser>('User', userSchema);

import { User } from './user.model';

export const createUser = async (userData: IUser) => {
  const user = await User.create(userData);
  return user;
};

export const getUsers = async () => {
  return await User.find();
};

import { Request, Response } from 'express';
import { createUser, getUsers } from './user.service';

export const createUserController = async (req: Request, res: Response) => {
  try {
    const user = await createUser(req.body);
    res.status(201).json(user);
  } catch (error) {
    res.status(500).json({ error: error.message });
  }
};

export const getUsersController = async (req: Request, res: Response) => {
  try {
    const users = await getUsers();
    res.status(200).json(users);
  } catch (error) {
    res.status(500).json({ error: error.message });
  }
};

import { z } from 'zod';

export const createUserSchema = z.object({
  body: z.object({
    name: z.string().min(1, 'Name is required'),
    email: z.string().email('Invalid email address'),
    password: z.string().min(6, 'Password must be at least 6 characters'),
  }),
});

import express from 'express';
import { createUserController, getUsersController } from './user.controller';

const router = express.Router();

router.post('/', createUserController);
router.get('/', getUsersController);

export const UserRoutes = router;

import express, { Application } from 'express';
import mongoose from 'mongoose';
import { UserRoutes } from './modules/user/user.router';

const app: Application = express();

app.use(express.json());

// Routes
app.use('/api/users', UserRoutes);

export default app;

import app from './app';

const PORT = 5000;
const DATABASE_URL = 'mongodb://localhost:27017/modular_system';

app.listen(PORT, async () => {
  console.log(`Server is running on port ${PORT}`);
  try {
    await mongoose.connect(DATABASE_URL);
    console.log('Database connected');
  } catch (error) {
    console.error('Database connection failed:', error);
  }
});

"scripts": {
  "start": "ts-node-dev src/server.ts"
}

npm start