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100 TypeScript Interview Questions and Answers

Web & Backend · 100 questions, each with a full written answer — free, no sign-up.

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Basic 20Intermediate 20Advanced 20Expert 20Guru 20

Basic

  1. What is TypeScript and how is it different from JavaScript?
  2. Can you list some benefits of using TypeScript?
  3. What are data types in TypeScript and can you provide examples of each?
  4. How do you install TypeScript and compile a .ts file?
  5. What are the different ways to declare variables in TypeScript?
  6. Can you explain the concept of ’interfaces’ in TypeScript?
  7. How does TypeScript handle null and undefined values?
  8. How do you define and call a function in TypeScript?
  9. Can you explain the concept of ’classes’ in TypeScript and how it supports Object-Oriented Programming (OOP)?
  10. What are ’enums’ in TypeScript and how can you use them?
  11. What are generics in TypeScript and why are they useful?
  12. What are modules in TypeScript and how do they help in organizing code?
  13. How can you define an array in TypeScript?
  14. What are ’tuples’ in TypeScript?
  15. How does TypeScript support optional parameters in function?
  16. What is ’any’ type in TypeScript and when should you use it?
  17. How would you perform Type Assertion in TypeScript?
  18. What is ’never’ type in TypeScript and what is its purpose?
  19. What is ’strict null checks’ in TypeScript and how does it help?
  20. What are access modifiers in TypeScript and what are their roles in class properties and methods?

Intermediate

  1. Can you explain the differences between ’let’, ’const’, and ’var’ in TypeScript?
  2. How does TypeScript support default parameters in functions?
  3. What is the use of namespaces in TypeScript and how do they help in code organization?
  4. Can you explain the concept of ’type guards’ in TypeScript?
  5. How does TypeScript support asynchronous programming? Can you provide an example using async/await?
  6. What are decorators in TypeScript and how can you use them?
  7. How do you handle exceptions in TypeScript? Can you give an example of try/catch/finally?
  8. What is the purpose of the ’readonly’ modifier in TypeScript?
  9. What is the ’unknown’ type in TypeScript and how is it different from ’any’ type?
  10. How do you create and use a static property in TypeScript?
  11. How would you use TypeScript with Node.js?
  12. Can you explain the difference between ’interface’ and ’type’ in TypeScript?
  13. How would you create and use an index type in TypeScript?
  14. How do you declare and use a tuple type in TypeScript?
  15. How does TypeScript handle optional chaining?
  16. Can you explain the concept of conditional types in TypeScript?
  17. How does the TypeScript compiler handle ambient declarations or ’d.ts’ files?
  18. What are mapped types in TypeScript and how can you use them?
  19. How do you create a private constructor in TypeScript and why would you want to do it?
  20. Can you explain the concept of ’type inference’ in TypeScript?

Advanced

  1. How can you use TypeScript with popular front-end frameworks like React or Angular?
  2. How do you define and use a union type in TypeScript?
  3. Can you explain the concept of ’higher order functions’ in TypeScript?
  4. How can you create and use mixin classes in TypeScript?
  5. Can you explain how to create a ’declaration merging’ in TypeScript?
  6. How do you work with third-party type definitions, such as DefinitelyTyped, in TypeScript?
  7. Can you explain the difference between ’type’ and ’interface’ when defining a function type?
  8. What is a discriminated union in TypeScript and how can you use it?
  9. Can you give an example of using a ’symbol’ type in TypeScript?
  10. What is the ’keyof’ operator in TypeScript and how can you use it?
  11. How can you implement an abstract class in TypeScript?
  12. Can you explain the concept of ’type narrowing’ in TypeScript?
  13. What is ’strict mode’ in TypeScript and what does it do?
  14. How do you use ’bigint’ in TypeScript and what are its use cases?
  15. What are utility types in TypeScript and can you provide examples of their usage?
  16. How can you use TypeScript to work with REST APIs?
  17. Can you explain how ’this’ works in TypeScript?
  18. What is ’type compatibility’ in TypeScript and how does it work?
  19. How do you configure a TypeScript project using ’tsconfig.json’?
  20. How can you handle module resolution in TypeScript?

Expert

  1. Can you describe how to set up and configure a build process for a TypeScript project?
  2. How can you use TypeScript with server-side frameworks like Express.js or NestJS?
  3. Can you explain the differences between ’as const’ vs ’const’ assertions in TypeScript?
  4. How do you handle transpilation of TypeScript into different versions of ECMAScript?
  5. What is the concept of ’declaration files’ in TypeScript and when should they be used?
  6. Can you explain how to use TypeScript with web workers?
  7. What are some strategies for migrating a large JavaScript codebase to TypeScript?
  8. Can you provide an example of using ’type predicates’ in TypeScript?
  9. How would you use TypeScript with a GraphQL API?
  10. Can you explain the difference between ’nominal typing’ and ’structural typing’ and how TypeScript relates to these concepts?
  11. How can you create a custom decorator in TypeScript?
  12. How do you optimize TypeScript compilation time for larger projects?
  13. What are some ways to handle interoperability between TypeScript and JavaScript in a codebase?
  14. Can you explain how to use mapped types with conditional types in TypeScript?
  15. What are some common performance issues you can encounter when using TypeScript and how can you mitigate them?
  16. Can you explain the concept of ’type widening’ and ’type narrowing’ in TypeScript?
  17. How would you use TypeScript with a package manager like npm or yarn?
  18. How do you use ’symbol’ and ’bigint’ in advanced TypeScript scenarios?
  19. Can you explain how to write unit tests for TypeScript code?
  20. What is the process of setting up a monorepo with TypeScript?

Guru

  1. Can you describe some architectural patterns for structuring large-scale TypeScript applications?
  2. How can you leverage TypeScript’s type system to enforce specific architectural constraints?
  3. What’s your approach to managing and evolving shared types in a large TypeScript codebase?
  4. How do you handle versioning of TypeScript declaration files in a large project?
  5. How would you handle collision of namespaces in TypeScript at scale?
  6. What considerations would you keep in mind while building a library to be consumed by other TypeScript projects?
  7. Can you discuss potential issues with TypeScript’s structural type system in large projects?
  8. Can you discuss the impact of enabling "strict" mode in TypeScript on a large scale project?
  9. How would you tackle performance optimization for TypeScript transpilation in a large, complex codebase?
  10. How do you enforce a consistent coding style and practices in a large TypeScript project?
  11. How can TypeScript be leveraged to improve the design of Domain Driven Design (DDD) or Clean Architecture?
  12. How do you manage the dependencies between different TypeScript projects in a monorepo?
  13. How can you leverage TypeScript’s type system for better error handling and failure recovery at runtime?
  14. Can you describe how to create custom type guards for complex types in TypeScript?
  15. What strategies would you employ to gradually adopt TypeScript in a large JavaScript project?
  16. How would you use TypeScript’s type system to enforce immutability?
  17. What are the best practices to handle ’any’ types in a large TypeScript project?
  18. Can you discuss some strategies for debugging complex type errors in TypeScript?
  19. How would you approach implementing multi-threading in a TypeScript project?
  20. How can TypeScript be used effectively with data science or machine learning libraries?
📕 Buy this interview preparation book: 100 TypeScript questions & answers — PDF + EPUB for $5
Reading is step one. Saying it out loud is the interview. Our AI interviewer calls your phone and runs a realistic TypeScript interview — then scores it.
📞 Practice TypeScript — free 15 min
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