Top TypeScript Interview Questions and Answers for 2025

This content originally appeared on DEV Community and was authored by Rishabh parmar

TypeScript has become one of the most widely used programming languages for front-end and back-end development. Its popularity continues to grow because it brings static typing, scalability, and robust developer experience to JavaScript. If you’re preparing for your next technical interview in 2025, having a strong grip on TypeScript concepts is crucial.

In this article, we’ll walk you through the top TypeScript interview questions and answers that will help you boost your confidence and stand out during the hiring process. These questions cover everything from the basics to advanced topics, making it easier for you to prepare thoroughly.

Why Learn TypeScript for Interviews?

Before diving into the questions, let’s quickly understand why TypeScript is so important in the developer ecosystem:

Better Code Quality: Strong typing prevents runtime errors.

Improved Developer Productivity: With IDE support, autocompletion, and type hints, coding becomes faster.

Scalability: TypeScript makes it easier to manage large-scale projects.

Industry Adoption: Popular frameworks like Angular, NestJS, and even React projects benefit greatly from TypeScript.

Now, let’s explore the most commonly asked questions.

Beginner-Level TypeScript Interview Questions

1. What is TypeScript?

Answer: TypeScript is an open-source programming language developed by Microsoft. It is a superset of JavaScript that adds optional static typing and advanced features like interfaces, enums, and generics. TypeScript code compiles down to plain JavaScript, which can run in any browser or JavaScript engine.

1. What are the main benefits of using TypeScript?

Answer:

Type safety through static type checking.

Enhanced code readability and maintainability.

Rich IDE support with autocompletion.

Early detection of bugs before runtime.

Compatibility with existing JavaScript code.

1. How does TypeScript differ from JavaScript?

Answer:

TypeScript supports static typing, while JavaScript is dynamically typed.

TypeScript provides additional features like interfaces, generics, and enums.

JavaScript code runs directly in the browser, while TypeScript must first be compiled into JavaScript.

1. Can you explain “any,” “unknown,” and “never” types in TypeScript?

Answer:

any: The most flexible type, allows a variable to hold any kind of value (not recommended for strict coding).

unknown: Safer than any because it forces developers to check the type before using it.

never: Represents values that should never occur, often used in functions that throw errors or have infinite loops.

1. What is the difference between interface and type in TypeScript?

Answer:

interface: Best suited for describing object shapes and contracts. They are extendable and can be merged.

type: Can alias primitive types, unions, and tuples, offering more flexibility but less extendability compared to interfaces.

Intermediate-Level TypeScript Interview Questions

1. What are generics in TypeScript?

Answer: Generics allow you to create reusable components that can work with various data types. They make functions, classes, and interfaces more flexible without sacrificing type safety.
Example:

function identity(value: T): T {
return value;
}

1. What is the difference between null and undefined in TypeScript?

Answer:

undefined: A variable that has been declared but not assigned a value.

null: An assigned value that represents “no value” or “empty.”
With --strictNullChecks, TypeScript enforces stricter handling of these values.

1. Explain “union” and “intersection” types with examples.

Answer:

Union type (|): A variable can hold values from multiple types.

let id: number | string;
id = 101;
id = "ABC";

Intersection type (&): Combines multiple types into one.

interface A { name: string; }
interface B { age: number; }
type Person = A & B; // must have both name and age

1. What are decorators in TypeScript?

Answer: Decorators are special functions that can modify the behavior of classes, methods, properties, or parameters. They are widely used in frameworks like Angular.
Example:

function Logger(target: Function) {
console.log(Class ${target.name} was created.);
}
@Logger
class Example {}

1. What is type inference in TypeScript?

Answer: TypeScript can automatically determine the type of a variable based on its initial value.
Example:

let count = 10; // inferred as number

Advanced-Level TypeScript Interview Questions

1. How does TypeScript handle asynchronous programming?

Answer: TypeScript supports async/await syntax with full type safety. Developers can define promise-based functions with strong typing, making code easier to read and debug.
Example:

async function fetchData(): Promise {
return "Data fetched";
}

1. Explain “mapped types” in TypeScript.

Answer: Mapped types allow you to create new types by transforming existing ones.
Example:

type ReadonlyType = {
readonly [K in keyof T]: T[K];
};

1. What is the difference between interface merging and namespace in TypeScript?

Answer:

Interface merging: Multiple declarations of the same interface are automatically combined.

Namespace: Used for logical grouping of related variables, classes, and functions.

1. How does TypeScript support React development?

Answer:

Provides type safety for props, state, and hooks.

Improves IDE support and debugging.

Helps prevent runtime errors in large React applications.

1. What are utility types in TypeScript?

Answer: TypeScript provides built-in utility types to manipulate types easily. Examples include:

Partial – Makes all properties optional.

Readonly – Makes all properties read-only.

Pick – Creates a type by picking specific keys.

Omit – Creates a type by omitting specific keys.

Bonus Tips for TypeScript Interviews

Understand the fundamentals of JavaScript – since TypeScript is a superset, a strong JS foundation helps.

Practice coding problems – many interviews include live coding rounds.

Work on small projects – build something practical like a to-do app in React with TypeScript.

Stay updated – new TypeScript releases bring improvements every year.

Final Thoughts

Preparing for a technical interview can feel overwhelming, but mastering the right set of questions can give you a competitive edge. This guide covered essential TypeScript interview questions and answers that you’re likely to face in 2025.

Whether you’re a beginner or an experienced developer, understanding these concepts will not only help you during interviews but also improve your real-world coding skills. Remember, beyond memorizing answers, focus on writing clean, type-safe, and scalable code.

With consistent practice and the right preparation, you’ll be ready to ace your next interview and showcase your TypeScript expertise.

This content originally appeared on DEV Community and was authored by Rishabh parmar