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Object-Oriented Programming 101

A comprehensive guide to mastering Object-Oriented Programming with TypeScript, from basic classes to advanced design patterns.

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Series Overview

This series teaches OOP through building real TypeScript applications—REST APIs, microservices, and domain models. Instead of abstract examples, you'll learn OOP concepts I use daily when architecting scalable backend systems.

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What You'll Learn

  • Part 1: Classes and Objects - Building Blocks - TypeScript class syntax, constructors, properties, methods, and creating object instances

  • Part 2: Encapsulation and Access Modifiers - Data Protection - Private/public/protected modifiers, getters/setters, and information hiding

  • Part 3: Inheritance and Polymorphism - Code Reuse - Extending classes, method overriding, abstract classes, and polymorphic behavior

  • Part 4: Interfaces and Composition - Flexible Design - TypeScript interfaces, composition over inheritance, dependency injection

  • Part 5: SOLID Principles and Design Patterns - Production-Ready Code - Applying SOLID principles and common design patterns in real applications

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Who This Is For

  • JavaScript/TypeScript developers wanting to master OOP concepts

  • Engineers building backend APIs, microservices, or domain-driven systems

  • Anyone who writes classes but wants to understand the deeper principles

  • Developers transitioning from procedural to object-oriented design

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Learning Philosophy

Each article demonstrates OOP through code I've written for production systems—user authentication services, payment processing, order management, API gateways. No contrived "Animal" or "Vehicle" examples. Just practical patterns that solve real problems.

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Prerequisites

  • Basic TypeScript/JavaScript knowledge

  • Understanding of functions and data structures

  • Familiarity with npm/Node.js

  • Willingness to think about code structure and design

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Tools Used

  • TypeScript: Primary language with strong OOP support

  • Node.js: Runtime environment

  • Real Projects: FastAPI-style Express apps, domain models, service layers

  • VS Code: Development environment

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Why OOP Matters

Early in my career, I wrote procedural code—functions manipulating data structures. As systems grew, code became unmaintainable. Functions were thousands of lines. Data validation scattered everywhere. Testing was a nightmare.

Learning OOP transformed how I structure code:

  • Classes organize related data and behavior together

  • Encapsulation hides implementation details

  • Inheritance reduces code duplication

  • Polymorphism makes code flexible and extensible

  • Interfaces define contracts for loose coupling

A well-designed class hierarchy can save thousands of lines of code and months of maintenance time.

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Series Structure

Each part builds on the previous, starting with basic class syntax and progressing to advanced design patterns. You can jump to specific topics, but following the sequence gives you the complete OOP foundation.

Ready to master object-oriented programming? Start with Part 1: Classes and Objects - Building Blocks.

Based on years of building TypeScript backend systems, from simple APIs to complex microservices with layered architectures.

PreviousPart 5: Advanced Querying, Aggregations, and Production Best PracticesNextPart 1: Classes and Objects - Building Blocks

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