Designing OOP TypeScript

When to use

• Creating new domain entities or value objects
• Refactoring procedural code into OOP
• Designing class hierarchies with SOLID principles

Core rules

1. Classes over functions: all behavior encapsulated in classes
2. Explicit access modifiers: public, protected, private always written
3. SRP: one responsibility per class, split when growing
4. Encapsulation: no public mutable fields, expose intent via methods
5. Immutability: value objects are readonly, entities use private state
6. SOLID: Single responsibility, Open/closed, Liskov, Interface segregation, Dependency inversion

Reference shape (TypeScript)