TypeScript Interview: 200 Questions and Answers

The book "TypeScript Interview: 200 Questions and Answers" is a practical guide for developers who want to confidently pass a technical interview and deepen their knowledge of TypeScript. The author has collected the most common and complex questions asked at interviews in Russian and international IT companies, and prepared detailed, structured answers with code examples.

What is the book about?

The book covers all key TypeScript topics:

• Typing basics: primitive types, objects, arrays, tuples, enums.
• Advanced types: union and intersection types, type guards, conditional types, mapped types, conditional types.
• Generics: generic functions, classes, interfaces, constraints, using keyof and infer.
• Classes and OOP: access modifiers, abstract classes, interfaces, mixins.
• Modules and namespaces: import/export, ambient declarations, working with external libraries.
• Decorators: class, method, property decorators, decorator parameters.
• Utility types: Partial, Required, Readonly, Pick, Omit, Exclude, Extract, NonNullable, ReturnType, Parameters, and others.
• Typing in real projects: working with Redux, React, Express, TypeORM, testing.
• Common mistakes and pitfalls: typing this, function overloading, strict typing, type compatibility.

Who is this book for?

• Junior developers — systematize knowledge, learn to answer basic and intermediate questions.
• Middle developers — fill gaps in advanced topics, learn non-obvious nuances of TypeScript.
• Team leads and mentors — can use the book as a reference for preparing their team.

What will the reader learn?

• How to properly type complex data structures and functions.
• How to use generics to create flexible and safe components.
• How to avoid common mistakes when working with types.
• How to explain TypeScript concepts clearly and confidently in an interview.
• How to solve typing problems in real time.

The book is structured on the principle of "question — answer — analysis." Each answer is accompanied by code, explanations, and possible variations of questions. This is not just a collection of cheat sheets, but a full-fledged TypeScript textbook focused on practice and interviews.

Why should you read this book? TypeScript is one of the most in-demand languages in web development. Knowledge of its nuances directly affects salary levels and the speed of receiving a job offer. The book will help not only prepare for an interview but also gain a deeper understanding of the JavaScript and TypeScript ecosystem.

Perfect for self-study and review before an interview. All examples are relevant for TypeScript 4.x and 5.