TypeScript Interview Questions and Answers

Here are some of the basic interview questions and answers asked in TypeScript interviews.

TypeScript Interview Questions and Answers

1. What is TypeScript?

Answer: TypeScript is a statically- superset of JavaScript that adds features to JavaScript to help developers write more robust and maintainable code.

2. What is the difference between TypeScript and JavaScript?

Answer: TypeScript is a superset of JavaScript that adds features to JavaScript to help developers write more robust and maintainable code. JavaScript has dynamic typing, but TypeScript has static typing.

3. How is TypeScript compiled?

Answer: TypeScript is compiled into JavaScript code using the TypeScript compiler.

4. What is a type in TypeScript?

Answer: A type in TypeScript refers to the type of a value, such as a number, string, or boolean.

5. In TypeScript, what distinguishes a type from an interface?

Answer: An interface in TypeScript is a way to describe the shape of an object, while a type is a way to describe the type of a value.

6. What is a class in TypeScript?

Answer: A class in TypeScript is a blueprint for creating objects that share the same properties and methods.

7. What is a module in TypeScript?

Answer: A module in TypeScript is a way to organize code into separate files and namespaces.

8. What is the difference between a namespace and a module in TypeScript?

Answer: A namespace in TypeScript is a way to group related code into a single global scope. A module is a way to organize code into separate files and namespaces.

9. What is a decorator in TypeScript?

Answer: A decorator in TypeScript is a special kind of declaration that can be attached to a class declaration, method, accessor, property, or parameter.

10. What is the purpose of a decorator in TypeScript?

Answer: The purpose of a decorator in TypeScript is to modify the behavior of a class or its members without having to modify the original source code.

11. What distinguishes a TypeScript abstract class from an interface?

Answer: An abstract class in TypeScript can have implementation details, while an interface cannot. An abstract class can also be extended, while an interface can be implemented.

12. What is a generic in TypeScript?

Answer: A generic in TypeScript is a type that can be used with multiple types.

13. What is a union type in TypeScript?

Answer: A union type in TypeScript allows a value to have more than one type.

14. What is an intersection type in TypeScript?

Answer: An intersection type in TypeScript allows a value to have multiple types.

15. What is a type assertion in TypeScript?

Answer: A type assertion in TypeScript is a way to tell the TypeScript compiler the type of a value.

16. What is a type guard in TypeScript?

Answer: A type guard in TypeScript is a way to narrow the type of a value based on a condition.

17. What is a type alias in TypeScript?

Answer: A type alias in TypeScript is a way to create a named alias for a type.

18. What is the difference between a type alias and an interface in TypeScript?

Answer: A type alias in TypeScript is more flexible than an interface because it can be used with any type, not just objects. A type alias can also be used to create union and intersection types.

19. What is a declaration file in TypeScript?

Answer: A declaration file in TypeScript is a file that describes the shape of a JavaScript module or library.

20. How is a declaration file used in TypeScript?

Answer: A declaration file is used by the TypeScript compiler to provide type information for JavaScript modules or libraries.

21. What is a type parameter in TypeScript?

Answer: A type parameter in TypeScript is a placeholder for a type that can be specified later.

22. What is the difference between an arrow and regular functions in TypeScript?

Answer: An arrow function in TypeScript is more concise than a regular function and does not require a separate this binding. Arrow functions also cannot be used as constructors.

23. What is an optional parameter in TypeScript?

Answer: An optional parameter in TypeScript is a parameter that can be omitted when calling a function.

24. What is a default parameter in TypeScript?

Answer: A default parameter in TypeScript is a parameter that has a default value that is used if no value is provided when calling the function.

25. What is a rest parameter in TypeScript?

Answer: A rest parameter in TypeScript is a parameter that allows a function to accept an indefinite number of arguments as an array.

26. What is a readonly property in TypeScript?

Answer: A readonly property in TypeScript is a property that can only be set once, either at initialization or in the constructor.

27. What is a private property in TypeScript?

Answer: A private property in TypeScript is a property that can only be accessed within the same class.

28. What is a protected property in TypeScript?

Answer: A protected property in TypeScript is a property that can only be accessed within the same class or its subclasses.

29. What is a public property in TypeScript?

Answer: A public property in TypeScript is a property that can be accessed from anywhere.

30. What is a getter in TypeScript?

Answer: A getter in TypeScript is a method that is used to retrieve the value of a property.

31. What is a setter in TypeScript?

Answer: A setter in TypeScript is a method that is used to set the value of a property.

32. What is an abstract method in TypeScript?

Answer: An abstract method in TypeScript is a method that does not have an implementation and must be implemented by a subclass.

33. What is an async function in TypeScript?

Answer: An async function in TypeScript is a function that returns a Promise and can use the await keyword to wait for other asynchronous functions to complete.

34. What is a Promise in TypeScript?

Answer: A Promise in TypeScript is an object that represents the eventual completion (or failure) of an asynchronous operation and allows for more readable and maintainable asynchronous code.

35. What is a callback function in TypeScript?

Answer: A callback function in TypeScript is a function that is passed as an argument to another function and is called when that function completes.

36. What is a higher-order function in TypeScript?

Answer: A higher-order function in TypeScript is a function that takes one or more functions as arguments or returns a function as its result.

37. What is the never type in TypeScript?

Answer: The never type in TypeScript represents a value that will never occur, such as the result of a function that always throws an error.

38. What is a type predicate in TypeScript?

Answer: A type predicate in TypeScript is a function that returns a boolean and is used to narrow the type of a value.

39. What is a type operator in TypeScript?

Answer: A type operator in TypeScript is a keyword or symbol that is used to manipulate types, such as the typeof operator or the keyof operator.

40. What is a tuple in TypeScript?

Answer: A tuple in TypeScript is an array with a fixed number of elements; each element can have a different type.

41. What is a namespace in TypeScript?

Answer: A namespace in TypeScript is a way to group related code into a single global scope.

42. What is a module in TypeScript?

Answer: A module in TypeScript is a way to organize code into separate files and namespaces.

43. What is the export keyword in TypeScript?

Answer: The export keyword in TypeScript is used to export functions, classes, variables, or interfaces from a module so they can be used in other modules.

44. What is the import keyword in TypeScript?

Answer: The import keyword in TypeScript is used to import functions, classes, variables, or interfaces from other modules.

45. What is a type alias in TypeScript?

Answer: A type alias in TypeScript is a way to give a name to a type that is used frequently throughout a codebase.

46. What is a type assertion in TypeScript?

Answer: A type assertion in TypeScript is a way to tell the compiler the type of a value when the compiler cannot infer it automatically.

47. What is a declaration file in TypeScript?

Answer: A declaration file in TypeScript is a file that contains type information for JavaScript code.

48. What is an interface in TypeScript?

Answer: An interface in TypeScript is a way to define the shape of an object, including its properties and methods.

49. What is a class in TypeScript?

Answer: A class in TypeScript is a blueprint for creating objects that encapsulate data and behavior.

50. What is inheritance in TypeScript?

Answer: Inheritance in TypeScript is a way to create a new class that is a modified version of an existing class, inheriting its properties and methods.

51. What is encapsulation in TypeScript?

Answer: Encapsulation in TypeScript is the concept of hiding the internal implementation of a class from external code, so that the class can be modified without affecting other parts of the codebase.

52. What is polymorphism in TypeScript?

Answer: Polymorphism in TypeScript is the ability of a class to take on multiple forms, depending on the context in which it is used.

53. What is a constructor in TypeScript?

Answer: A constructor in TypeScript is a special method that is called when an object of a class is created, and is used to set the initial state of the object.

54. What is the super keyword in TypeScript?

Answer: The super keyword in TypeScript is used to call a method or constructor from the parent class.

55. What is a static property or method in TypeScript?

Answer: A static property or method in TypeScript is a property or method that belongs to the class itself, rather than to instances of the class.

56. What is a decorator in TypeScript?

Answer: A decorator in TypeScript is a way to modify the behavior of a class, method, or property, by adding metadata.

57. What is a generic type in TypeScript?

Answer: A generic type in TypeScript is a way to create a type that can be used with multiple types.

58. What distinguishes type from interface in TypeScript?

Answer: The interface keyword in TypeScript is used to define the shape of an object, while the type keyword is used to create a type alias for a specific type.

59. What is the difference between private and protected in TypeScript?

Answer: The private keyword in TypeScript makes a property or method accessible only within the same class, while the protected keyword allows access within the same class and its subclasses.

60. What is the difference between var, let, and const in TypeScript?

Answer: The var keyword in TypeScript is used to declare a variable with function scope, while the let and const keywords declare variables with block scope. The let keyword allows the variable to be reassigned, while the const keyword creates a variable with a value that cannot be changed.

Summary

Hope this article helped you in learning basic TypeScript Interview Questions and Answers. Do not forget to check our advanced level of TypeScript Interview