TypeScript Questions and Answers for Viva

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Interview Question and Answer of TypeScript

Question-1. What is TypeScript?

Answer-1: TypeScript is a strongly typed superset of JavaScript developed by Microsoft, compiled to JavaScript.

Question-2. What are the key features of TypeScript?

Answer-2: Key features include static typing, interfaces, generics, classes, and ES6+ features.

Question-3. What is the difference between TypeScript and JavaScript?

Answer-3: TypeScript adds static types, interfaces, and compile-time checks to JavaScript.

Question-4. How do you install TypeScript?

Answer-4: Install using npm: npm install -g typescript.

Question-5. What is the file extension for TypeScript?

Answer-5: TypeScript files use the .ts extension.

Question-6. How do you compile a TypeScript file?

Answer-6: Use the tsc command: tsc filename.ts.

Question-7. What is the TypeScript compiler?

Answer-7: The TypeScript compiler, tsc, converts TypeScript code into JavaScript.

Question-8. What are TypeScript interfaces?

Answer-8: Interfaces define the structure of objects, enforcing property names and types.

Question-9. What is the any type in TypeScript?

Answer-9: The any type disables type checking, allowing a variable to hold any value.

Question-10. What is the unknown type in TypeScript?

Answer-10: The unknown type is a safer alternative to any, requiring a type check before usage.

Question-11. What is the difference between any and unknown?

Answer-11: any allows unchecked operations; unknown requires explicit type checks before usage.

Question-12. What is a union type in TypeScript?

Answer-12: Union types allow variables to hold values of multiple types. Syntax: `type A = string

Question-13. What are enums in TypeScript?

Answer-13: Enums define named constants. Example: enum Color { Red, Green, Blue }.

Question-14. What is type inference in TypeScript?

Answer-14: TypeScript automatically determines the type of a variable based on its value.

Question-15. What is the never type in TypeScript?

Answer-15: The never type represents values that never occur, used for functions that throw or never return.

Question-16. What is the void type in TypeScript?

Answer-16: The void type indicates a function does not return a value.

Question-17. What is the difference between interface and type?

Answer-17: Both can define object types, but type is more flexible and supports unions and intersections.

Question-18. What are TypeScript generics?

Answer-18: Generics allow functions, classes, and interfaces to operate with various types. Syntax: .

Question-19. How do you declare a tuple in TypeScript?

Answer-19: Tuples are declared using arrays with fixed types: [string, number].

Question-20. What is readonly in TypeScript?

Answer-20: readonly prevents modification of properties or variables.

Question-21. How do you implement inheritance in TypeScript?

Answer-21: Use the extends keyword. Example: class Child extends Parent { }.

Question-22. What are TypeScript decorators?

Answer-22: Decorators are special functions applied to classes, methods, or properties to modify their behavior.

Question-23. What is type assertion in TypeScript?

Answer-23: Type assertion tells the compiler the type of a variable. Syntax: variable as Type.

Question-24. How do you handle null and undefined in TypeScript?

Answer-24: Use union types (`string

Question-25. What is the keyof operator in TypeScript?

Answer-25: keyof gets the keys of a type as a union of string literals.

Question-26. How do you create a module in TypeScript?

Answer-26: Use export and import keywords to define and consume modules.

Question-27. What is the difference between abstract class and interface?

Answer-27: An abstract class can have implementations; interfaces cannot but define structure contracts.

Question-28. What are mapped types in TypeScript?

Answer-28: Mapped types create new types by transforming properties of an existing type. Example: Partial.

Question-29. What is the purpose of the Partial utility type?

Answer-29: Partial makes all properties of T optional.

Question-30. What is the purpose of the Readonly utility type?

Answer-30: Readonly makes all properties of T immutable.

Question-31. What are utility types in TypeScript?

Answer-31: Utility types like Partial, Readonly, and Pick simplify type transformations.

Question-32. What is the Pick utility type?

Answer-32: Pick creates a type with selected properties K from type T.

Question-33. What is the Record utility type?

Answer-33: Record creates a type with keys K and values T.

Question-34. What is the Exclude utility type?

Answer-34: Exclude removes types U from type T.

Question-35. What is the Omit utility type in TypeScript?

Answer-35: Omit creates a type by excluding properties K from type T.

Question-36. What is a namespace in TypeScript?

Answer-36: Namespaces group related code to avoid global scope pollution.

Question-37. What is the purpose of the extends keyword in TypeScript?

Answer-37: extends is used in generics and classes for inheritance or type constraints.

Question-38. What are inline types in TypeScript?

Answer-38: Inline types define types directly where they're used, without creating reusable type aliases or interfaces.

Question-39. What is the strict flag in TypeScript?

Answer-39: The strict flag enables all strict type-checking options.

Question-40. How does TypeScript support React?

Answer-40: TypeScript supports React using .tsx files, adding type safety to components and props.

Question-41. What is the difference between export and default export?

Answer-41: export can export multiple members; default export exports a single default member.

Question-42. What is the typeof operator in TypeScript?

Answer-42: typeof gets the type of a variable or object.

Question-43. What is the as keyword in TypeScript?

Answer-43: The as keyword is used for type assertions.

Question-44. What is the globalThis object in TypeScript?

Answer-44: globalThis provides a standard way to access the global object across environments.

Question-45. What is the purpose of TypeScript's config.json file?

Answer-45: The tsconfig.json file configures TypeScript compilation options.

Question-46. What is module augmentation in TypeScript?

Answer-46: Module augmentation adds new declarations to an existing module.

Question-47. What is the outDir option in tsconfig.json?

Answer-47: The outDir option specifies the output directory for compiled files.

Question-48. What is the difference between declare and export?

Answer-48: declare adds ambient declarations; export makes members accessible to other modules.

Question-49. What is the include option in tsconfig.json?

Answer-49: The include option specifies which files or directories to compile.

Question-50. How do you define optional properties in TypeScript?

Answer-50: Use ? after the property name. Example: propertyName?: string;.

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TypeScript Questions and Answers for Viva

Interview Question and Answer of TypeScript

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