Advanced TypeScript

TypeScript isn't just "JavaScript with Colon-types." It is a sophisticated type-programming language. In large-scale teams, Type Safety is what prevents production-breaking bugs during refactoring.

1. Generics: The Reusability Engine

Generics allow you to create components and functions that work with many types while retaining full type safety. Think of it as passing a 'Type' as a variable.

interface ApiResponse<T> {
    data: T;
    error: string | null;
}

2. Conditional & Mapped Types

TypeScript allows you to transform one type into another. Partial<T> turns all properties optional. ReturnType<T> extracts the result of a function. You can even use infer to extract types from deep within nested structures.

4. Interview Mastery

Q: "What is the difference between 'unknown' and 'any'?"

Architect Answer: "`any` is a total safety shut-off. It tells TypeScript to ignore the variable completely. `unknown` is the type-safe version. It says 'We don't know what this is yet.' You cannot use an `unknown` variable until you **Narrow** it using a type guard (e.g., `if (typeof x === "string")`). Professional architects should almost always use `unknown` for dynamic data like API responses."