🧠 12-Week Deep OOP Mastery Program (with TypeScript + Express.js)

This repository documents a 12-week advanced Object-Oriented Programming (OOP) roadmap, adapted into a class-based backend architecture using TypeScript, Express.js, and modern patterns like Clean Code, SOLID principles, and Design Patterns. This codebase includes:

• Highly structured backend with ESLint, Prettier, and strict tsconfig.json
• A powerful path aliasing system for modular architecture
• Deep exploration of OOP concepts
• Practical implementation of design patterns and system design

🧩 Note: There aren't isolated tutorials for each week. Instead, the full backend server composes all the weekly concepts into a unified, production-grade architecture. However, design pattern examples and learning materials are organized separately inside the @classes folder to teach and demonstrate each pattern in isolation.

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📁 Folder Aliases (tsconfig.json)

"paths": {
  "@/*": ["*"],
  "@config": ["src/config"],
  "@controllers/*": ["controllers/*"],
  "@exceptions/*": ["exceptions/*"],
  "@interfaces/*": ["interfaces/*"],
  "@middlewares/*": ["middlewares/*"],
  "@models/*": ["models/*"],
  "@routes/*": ["routes/*"],
  "@schemas/*": ["schemas/*"],
  "@services/*": ["services/*"],
  "@utils/*": ["utils/*"],
  "@classes/*": ["classes/*"]
}

📦 What lives in each path?

Alias	Description
@config	Environment variables, database config, server setup
@controllers/*	Request handlers using class-based controller logic
@exceptions/*	Custom error classes (e.g. NotFound, Unauthorized)
@interfaces/*	TypeScript interfaces and types shared across app
@middlewares/*	Express middlewares (auth, error handling, logging)
@models/*	Mongoose models and schemas
@routes/*	Route definitions mapped to controller methods
@schemas/*	Zod validation schemas
@services/*	Business logic classes (e.g. UserService, AuthService)
@utils/*	Utility functions, helpers, formatters, loggers
@classes/*	Design patterns classes, starting from Creational to Behavioral and teaching patterns

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📚 Week-by-Week Curriculum

✅ Week 1: OOP Basics (Encapsulation, Classes, Instances)

Note: Services, Controllers, App and etc.. all use the OOP basic methods below

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• Create real-world class models
• Understand private, protected, public
• Learn getters methods, setters methods, constructor

✅ Week 2: Inheritance & Polymorphism

Note: Controllers, Classes use the OOP basic methods below

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• Class hierarchies: Animal -> Dog/Cat
• Method overriding
• Use interfaces and abstract classes

✅ Week 3: SOLID Principles

Note: Controllers, Services, Routes, and Classes all use the OOP basic methods below

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• Single Responsibility
• Open/Closed
• Liskov Substitution
• Interface Segregation
• Dependency Inversion

✅ Week 4: Composition Over Inheritance

Note: Controllers, Services, Routes, and Classes all use the OOP basic methods below

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• Mixins with Object.assign
• Strategy pattern
• Favor small components over rigid inheritance trees

✅ Week 5: Creational Design Patterns

Note: Classes (Creational.class.ts) use the OOP basic methods below

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• Factory Pattern (e.g. UserFactory)
• Builder Pattern (ReportBuilder)
• Singleton (DBConnection)
• Abstract Factory

✅ Week 6: Structural Design Patterns

Note: Classes (Structural.class.ts) use the OOP basic methods below

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• Adapter (LoggerAdapter)
• Decorator (TimestampLogger)
• Composite (ShapeGroup)
• Proxy (LoggingProxy)

✅ Week 7: Behavioral Design Patterns

Note: Classes (Behavioral.class.ts) use the OOP basic methods below

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• Observer (Event system)
• Command (Encapsulate request logic)
• Strategy (Pluggable behaviors)
• State (Finite state machine in backend)

✅ Week 8: Domain Modeling + Value Objects

• Domain-Driven Design intro
• Encapsulate logic into Value Objects (e.g. Money, Email, PhoneNumber)

✅ Week 9: Repositories & Aggregates

• Persistence layer abstraction
• Domain Aggregate root enforcement (e.g. Order)

✅ Week 10: Event-Driven Architecture

• Internal domain events
• Event dispatchers, listeners
• Async patterns with Redis/Queue

✅ Week 11: Advanced Types + Refactoring

• Utility types, template literals, enums, generics
• Refactor messy classes into clean interfaces and reusable components

✅ Week 12: Testing OOP Systems

• Unit testing services, repositories, controllers using Jest
• Mocks, spies, and stubs
• Full coverage of SOLID and patterns under test

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✅ Prerequisites

• TypeScript (strict mode)
• Node.js / Express.js
• OOP fundamentals in JS or another language
• Familiarity with async/await, Promises
• Familiarity mongodb and mongoose schemas
• Familiarity with zod for validation
• Familiarity with JWT

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📌 Example Command Scripts (package.json)

"scripts": {
    "dev": " cross-env NODE_ENV=development ts-node-dev --respawn --transpile-only --require tsconfig-paths/register src/server.ts",
    "start": "npm run build && cross-env NODE_ENV=production node dist/server.js",
    "build": "swc src -d dist --source-maps --copy-files",
    "build:tsc": "tsc && tsc-alias",
    "lint": "eslint  src/**/*.ts",
    "lint:fix": "eslint src/**/*.ts --fix"
}

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🧱 Node.js TypeScript Starter (SWC + ts-node-dev)

A clean, production-ready Node.js starter with TypeScript, SWC, ts-node-dev, and support for path aliases.

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📦 Project Scripts

🛠 Development

Run the project in development mode using ts-node-dev with automatic restarts on changes:

npm run dev

Uses: ts-node-dev with path aliases and environment set to development.

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⚙️ Build (Production)

Transpile your TypeScript code to JavaScript using SWC and output it to the dist/src directory:

npm run build

Uses: swc to transpile everything from src/ into dist/src with source maps and file copying.

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🚀 Start (Production)

First builds the app, then runs the compiled code in production mode:

npm start

Alias for: npm run build && NODE_ENV=production node dist/src/server.js

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✅ Linting

Check for code quality and lint errors:

npm run lint

Automatically fix linting issues:

npm run lint:fix

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🧪 Test (Coming Soon)

Add your test script here once you integrate the testing library Jest.

npm run test

🧪 Testing setup will be added soon.

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🏁 Final Deliverables

• @/classes/creational-patterns
• @/classes/structural-patterns
• @/classes/behavioral-patterns
• @/classes/domain-modeling
• /event-driven
• /test-suite

Build your own advanced backend playground and master Object-Oriented design with real architecture.

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👨‍🏫 Inspired By:

• Refactoring.Guru
• TypeScript Deep Dive
• Domain-Driven Design (Vaughn Vernon / Eric Evans)
• Clean Architecture by Uncle Bob

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