100 Essential JavaScript Interview Questions for Aspiring Developers

Master JavaScript for Your Next Interview with These 100 Essential Questions Covering Basics to Advanced Concepts

Welcome to RemoteCoded! If you're preparing for a JavaScript interview, you're in the right place. We've compiled a comprehensive list of 100 essential JavaScript interview questions to help you get ready. These questions cover a range of topics from the basics to more advanced concepts. Good luck with your preparation!

Basic JavaScript Questions

1. What is JavaScript, and where is it used?

2. Explain the difference between JavaScript and Java.

3. How do you include JavaScript in an HTML file?

4. What are the data types supported by JavaScript?

5. Explain the concept of var, let, and const keywords.

6. What is hoisting in JavaScript?

7. Describe the use of this keyword.

8. What are JavaScript closures?

9. How do you create a function in JavaScript?

10. Explain the concept of an anonymous function.

11. What is an Immediately Invoked Function Expression (IIFE)?

12. Describe the differences between == and ===.

13. What are truthy and falsy values in JavaScript?

14. How do you create arrays in JavaScript?

15. Explain array methods such as push(), pop(), shift(), and unshift().

16. What is the difference between null and undefined?

17. How do you create objects in JavaScript?

18. What are object prototypes?

19. How does prototypal inheritance work?

20. Explain the concept of scope and scope chain.

Intermediate JavaScript Questions

21. What is an event in JavaScript?

22. How do you handle events in JavaScript?

23. Explain event delegation.

24. What are higher-order functions?

25. How do you use map(), filter(), and reduce() methods?

26. What is the difference between call(), apply(), and bind()?

27. How do you create and use promises?

28. What are async/await functions?

29. Explain the concept of a callback function.

30. What is AJAX and how do you use it in JavaScript?

31. How do you handle errors in JavaScript?

32. What is the purpose of the try...catch statement?

33. How do you debug JavaScript code?

34. What are modules in JavaScript?

35. How do you export and import modules?

36. Explain the difference between default and named exports.

37. What is the Document Object Model (DOM)?

38. How do you manipulate the DOM?

39. What are JavaScript timers? Explain setTimeout() and setInterval().

40. How do you make HTTP requests in JavaScript?

Advanced JavaScript Questions

41. What is event bubbling and capturing?

42. Explain the concept of debouncing and throttling.

43. What are service workers?

44. How do you use the Fetch API?

45. Explain the concept of Single Page Applications (SPA).

46. What are Web Components?

47. How do you create a custom element?

48. Explain the concept of Shadow DOM.

49. What is the difference between localStorage, sessionStorage, and cookies?

50. How do you use WebSockets?

51. What is the difference between synchronous and asynchronous code?

52. Explain the concept of a JavaScript engine.

53. What are Generators in JavaScript?

54. How do you use the yield keyword?

55. What is the event loop in JavaScript?

56. Explain the concept of microtasks and macrotasks.

57. What is memory management in JavaScript?

58. How does garbage collection work?

59. What is the purpose of the Symbol data type?

60. Explain the concept of immutability in JavaScript.

Expert JavaScript Questions

61. What are proxies in JavaScript?

62. How do you create and use a proxy?

63. What is the Reflect API?

64. How do you handle cross-origin requests?

65. Explain the Same-Origin Policy.

66. What is a Content Security Policy (CSP)?

67. How do you implement security best practices in JavaScript?

68. What are Web Workers?

69. How do you use Web Workers for multithreading?

70. Explain the concept of progressive web apps (PWAs).

71. How do you create a PWA?

72. What is the difference between frontend and backend JavaScript?

73. How do you use Node.js?

74. What are npm and yarn?

75. How do you manage dependencies in JavaScript projects?

76. What is the purpose of package.json?

77. How do you set up a build process using Webpack?

78. What are JavaScript frameworks and libraries?

79. Explain the differences between React, Angular, and Vue.js.

80. How do you manage state in a JavaScript application?

Specialized JavaScript Questions

81. What is functional programming in JavaScript?

82. How do you use pure functions?

83. Explain the concept of currying.

84. What is memoization?

85. How do you use the reduce method for advanced data manipulation?

86. What is the Observer pattern?

87. How do you implement the Observer pattern in JavaScript?

88. What are design patterns in JavaScript?

89. Explain the Singleton pattern.

90. How do you use the Module pattern?

91. What is test-driven development (TDD)?

92. How do you write unit tests in JavaScript?

93. What are testing frameworks like Jest and Mocha?

94. How do you mock data for testing?

95. Explain the concept of integration testing.

96. How do you perform end-to-end testing?

97. What are best practices for code organization in JavaScript?

98. How do you ensure code quality in JavaScript projects?

99. What are JavaScript linting tools?

100. How do you use ESLint for static code analysis?

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We hope these questions help you in your JavaScript interview preparation. Whether you're just starting out or looking to deepen your knowledge, practicing these questions will give you a solid foundation in JavaScript programming. Stay tuned to RemoteCoded for more insightful articles and resources!