100 Javascript Interview Questions

Here is the list of 100 javascript interview questions

1. What is JavaScript?
2. What are the data types supported in JavaScript?
3. What is the difference between null and undefined in JavaScript?
4. What is the difference between == and === in JavaScript?
5. What are the different ways to declare a variable in JavaScript?
6. How do you check if a variable is an array in JavaScript?
7. How do you check if a variable is an object in JavaScript?
8. What is the difference between let and var in JavaScript?
9. What is the use of the “use strict” directive in JavaScript?
10. What are the different ways to create objects in JavaScript?
11. What is the difference between a function declaration and a function expression in JavaScript?
12. What is a closure in JavaScript?
13. What is the difference between call and apply methods in JavaScript?
14. What is the difference between bind and call methods in JavaScript?
15. What is hoisting in JavaScript?
16. What is the prototype in JavaScript?
17. How does inheritance work in JavaScript?
18. What is the difference between classical and prototypal inheritance in JavaScript?
19. What is the difference between a callback and a promise in JavaScript?
20. What is the event loop in JavaScript?
21. What are the different types of error in JavaScript?
22. What is the try-catch block in JavaScript?
23. What is the difference between throw and throw new Error in JavaScript?
24. What is the purpose of the finally block in JavaScript?
25. What is the difference between synchronous and asynchronous code in JavaScript?
26. What is the purpose of the setTimeout function in JavaScript?
27. What is the purpose of the setInterval function in JavaScript?
28. What is the difference between innerHTML and outerHTML in JavaScript?
29. What is the difference between innerText and textContent in JavaScript?
30. What is the purpose of the document object in JavaScript?
31. What is the purpose of the window object in JavaScript?
32. What is the purpose of the navigator object in JavaScript?
33. What is the purpose of the location object in JavaScript?
34. What is the purpose of the history object in JavaScript?
35. What is the difference between querySelector and getElementById in JavaScript?
36. What is the difference between clientHeight and offsetHeight in JavaScript?
37. What is the purpose of the getBoundingClientRect method in JavaScript?
38. What is the purpose of the scrollLeft and scrollTop properties in JavaScript?
39. What is the purpose of the onmouseover and onmouseout events in JavaScript?
40. What is the purpose of the onload and onunload events in JavaScript?
41. What is the purpose of the onclick event in JavaScript?
42. What is the purpose of the onsubmit event in JavaScript?
43. What is the purpose of the onkeydown and onkeyup events in JavaScript?
44. What is the purpose of the onscroll event in JavaScript?
45. What is the purpose of the onresize event in JavaScript?
46. What is the difference between the push and unshift methods in JavaScript arrays?
47. What is the difference between the pop and shift methods in JavaScript arrays?
48. What is the purpose of the splice method in JavaScript arrays?
49. What is the purpose of the slice method in JavaScript arrays?
50. What is the purpose of the map method in JavaScript arrays?
51. What is the purpose of the filter method in JavaScript arrays?
52. What is the purpose of the reduce method in JavaScript arrays?
53. What is the purpose of the sort method in JavaScript arrays?
54. What is the purpose of the concat method in JavaScript arrays?
55. What is the difference between a deep and a shallow copy in JavaScript?
56. What is the purpose of the JSON.stringify method in JavaScript?
57. What is the purpose of the JSON.parse method in JavaScript?
58. What is the difference between local and session storage in JavaScript?
59. What is the purpose of the XMLHttpRequest object in JavaScript?
60. What is the purpose of the fetch API in JavaScript?
61. What is the difference between async/await and promises in JavaScript?
62. What is the purpose of the spread operator in JavaScript?
63. What is the purpose of the rest parameter in JavaScript?
64. What is the purpose of the arrow function in JavaScript?
65. What is the purpose of the template literals in JavaScript?
66. What is the purpose of the destructuring assignment in JavaScript?
67. What is the difference between var, let, and const in JavaScript?
68. What is the purpose of the Symbol data type in JavaScript?
69. What is the purpose of the Map data structure in JavaScript?
70. What is the purpose of the Set data structure in JavaScript?
71. What is the purpose of the WeakMap data structure in JavaScript?
72. What is the purpose of the WeakSet data structure in JavaScript?
73. What is the purpose of the Proxy object in JavaScript?
74. What is the purpose of the Reflect object in JavaScript?
75. What is the purpose of the Object.freeze method in JavaScript?
76. What is the purpose of the Object.seal method in JavaScript?
77. What is the difference between call stack and event loop in JavaScript?
78. What is the difference between the document and window objects in JavaScript?
79. What is the purpose of the FormData object in JavaScript?
80. What is the purpose of the FileReader object in JavaScript?
81. What is the purpose of the Blob object in JavaScript?
82. What is the purpose of the URLSearchParams object in JavaScript?
83. What is the purpose of the Intl object in JavaScript?
84. What is the purpose of the Date object in JavaScript?
85. What is the purpose of the Math object in JavaScript?
86. What is the purpose of the parseInt function in JavaScript?
87. What is the purpose of the parseFloat function in JavaScript?
88. What is the difference between == and != in JavaScript?
89. What is the difference between > and >= in JavaScript?
90. What is the difference between < and <= in JavaScript?
91. What is the purpose of the isNaN function in JavaScript?
92. What is the purpose of the isFinite function in JavaScript?
93. What is the purpose of the Math.random function in JavaScript?
94. What is the purpose of the Math.floor function in JavaScript?
95. What is the purpose of the Math.ceil function in JavaScript?
96. What is the purpose of the Math.round function in JavaScript?
97. What is the purpose of the toLocaleString method in JavaScript?
98. What is the purpose of the toString method in JavaScript?
99. What is the purpose of the valueOf method in JavaScript?
100. What is the purpose of the Object.keys method in JavaScript?

I hope these 100 Javascript interview questions will help you prepare well for your Javascript interview. Good luck!