Generics let you write functions that work with many types while preserving the type relationship between input and output. Instead of function identity(x: any): any, you write function identity<T>(x: T): T — and TypeScript understands that whatever you pass in comes back out with the same type. Generics are the mechanism behind Array<T>, Promise<T>, Map<K,…

Classes have two sides: the instance side — properties and methods that live on each object created with new — and the static side — properties and methods that live on the class itself. Static members belong to the class, not to any instance. They’re used for factory methods, shared constants, counters, caches, and utility…

Getters and setters are methods that look like properties. You define get name() and set name(value), and callers use obj.name — no parentheses, no explicit function call. Under the hood, the getter or setter runs. TypeScript adds type checking on both sides: the getter’s return type and the setter’s parameter type. They’re the tool for…

Inheritance is how one class reuses and extends another — a child class gets the parent’s members and can add or override them. Polymorphism is what that enables at use time — the same call behaves differently depending on the actual object, without the caller knowing or caring which subclass it is. Together they’re the…

TypeScript gives you two ways to define a contract that other classes must fulfill: abstract classes and interfaces. They overlap in purpose — both describe a shape that implementations must satisfy — but they work differently and suit different situations. An abstract class is a real class that can’t be instantiated, can hold implementation, and…