Top 50 TypeScript Interview Questions

Mastering TypeScript interviews requires answering fundamental type system questions, explaining compiler behaviors, and demonstrating production problem-solving skills.

1. Introduction & Architecture

2. Deep Dive & Core Concepts

Key Areas Tested in TS Interviews: 1. Type Safety & Narrowing: Difference between any, unknown, never, and custom type predicates. 2. Structural vs Nominal: Why TypeScript uses structural typing and how to simulate nominal typing using Branded Types. 3. Generics & Inference: Constraints (extends), conditional types, and infer pattern matching. 4. Configuration & Modules: strictNullChecks, noImplicitAny, ES Modules vs Namespaces.

3. Basic Code Example

4. Advanced Production Patterns

5. Interactive Code Playground

type User = { id: string; name: string };
function validateUser(obj: any): obj is User {
  return typeof obj === "object" && obj !== null && "id" in obj && "name" in obj;
}
console.log(validateUser({ id: "1", name: "Alice" }));

6. Common Pitfalls & Edge Cases

7. Interview Q&A & Quizzes

Q: What is the purpose of the 'satisfies' operator introduced in TS 4.9?

A: It validates that an object conforms to a type signature without widening or losing the specific inferred literal types of the object's properties.

8. Summary Comparison Table