JavaScript Coding Questions

As a Front-End developer, JavaScript is the core skill of everything

Sort: most accepted

1. implement curry()JavaScript easy
14679 accepted
3. implement Array.prototype.flat()JavaScript easy
12102 accepted
4. implement basic throttle()JavaScript Lodash medium
9549 accepted
6. implement basic debounce()JavaScript Lodash easy
8228 accepted
19. find corresponding node in two identical DOM tree JavaScript easy
6846 accepted
16. create an Event Emitter JavaScript medium
6539 accepted
17. Create a simple store for DOM element JavaScript easy
4987 accepted
2. implement curry() with placeholder support JavaScript medium
4775 accepted
14. Implement a general memoization function - `memo()`JavaScript medium
4718 accepted
11. what is Composition? create a pipe()JavaScript easy
4667 accepted
28. implement clearAllTimeout()JavaScript easy
4403 accepted
18. Improve a function JavaScript easy
4119 accepted
32. implement `Promise.all()`JavaScript medium
4095 accepted
58. get DOM tree height JavaScript Algorithm DOM medium
3900 accepted
8. can you shuffle() an array?JavaScript easy
3557 accepted
10. first bad version JavaScript Algorithm medium
3352 accepted
7. implement debounce() with leading & trailing option JavaScript Lodash medium
3349 accepted
23. create a sum()JavaScript easy
3327 accepted
9. decode message JavaScript medium
3326 accepted
151. implement Array.prototype.map()JavaScript medium
3285 accepted
5. implement throttle() with leading & trailing option JavaScript Lodash medium
3208 accepted
15. implement a simple DOM wrapper to support method chaining like jQuery JavaScript easy
2922 accepted
162. find the single integer JavaScript Algorithm easy
2796 accepted
165. remove characters Algorithm easy
2640 accepted
25. Reorder array with new indexes JavaScript Algorithm easy
2606 accepted
113. Virtual DOM I JavaScript Algorithm DOM medium
2588 accepted
159. implement promisify()JavaScript medium
2514 accepted
155. create a count function JavaScript easy
2497 accepted
167. Intersection of unsorted arrays JavaScript Algorithm easy
2406 accepted
33. implement `Promise.allSettled()`JavaScript medium
2383 accepted
148. create a counter object JavaScript easy
2311 accepted
35. implement `Promise.race()`JavaScript easy
2284 accepted
161. toBe() or not.toBe()JavaScript medium
2273 accepted
29. implement async helper - `sequence()`JavaScript medium
2259 accepted
34. implement `Promise.any()`JavaScript medium
2230 accepted
154. Two-way binding JavaScript DOM easy
2215 accepted
68. get DOM tags JavaScript Algorithm DOM medium
2186 accepted
104. Traverse DOM level by level JavaScript Algorithm DOM easy
2084 accepted
91. invert a binary tree JavaScript Algorithm easy
1944 accepted
92. throttle Promises JavaScript medium
1942 accepted
89. Next Right Sibling JavaScript DOM easy
1892 accepted
57. create an Observable JavaScript medium
1846 accepted
64. auto-retry Promise on rejection JavaScript medium
1813 accepted
39. implement range()JavaScript easy
1775 accepted
13. Implement a Queue by using Stack JavaScript Algorithm medium
1755 accepted
110. serialize and deserialize binary tree JavaScript Algorithm medium
1734 accepted
146. implement Array.prototype.reduce()JavaScript medium
1730 accepted
26. implement Object.assign()JavaScript medium
1600 accepted
67. create your own Promise JavaScript medium
1565 accepted
157. semver compare JavaScript easy
1520 accepted
60. create your own `new` operator JavaScript easy
1477 accepted
30. implement async helper - `parallel()`JavaScript medium
1451 accepted
12. implement Immutability helper JavaScript medium
1439 accepted
20. Detect data type in JavaScript JavaScript medium
1424 accepted
63. create `_.cloneDeep()`JavaScript Algorithm Lodash medium
1407 accepted
37. implement Binary Search (unique)JavaScript easy
1403 accepted
56. call APIs with pagination JavaScript medium
1326 accepted
21. implement JSON.stringify()JavaScript medium
1312 accepted
46. implement `_.once()`JavaScript Lodash medium
1293 accepted
145. most frequently occurring character JavaScript easy
1291 accepted
47. reverse a linked list JavaScript Algorithm easy
1285 accepted
158. Previous Left Sibling JavaScript DOM medium
1283 accepted
31. implement async helper - `race()`JavaScript easy
1255 accepted
163. integer to roman numerals JavaScript Algorithm easy
1247 accepted
118. Virtual DOM II - createElement JavaScript easy
1246 accepted
61. create your own `Function.prototype.call`JavaScript medium
1225 accepted
123. implement Promise.prototype.finally()JavaScript medium
1223 accepted
168. move zeros JavaScript Algorithm medium
1176 accepted
176. undefined to null JavaScript medium
1125 accepted
40. implement Bubble Sort JavaScript Algorithm easy
1109 accepted
133. roman numerals to integer JavaScript easy
1096 accepted
53. write your own `extends` in es5 JavaScript medium
1075 accepted
94. implement your own `Object.create`JavaScript easy
1074 accepted
122. implement memoizeOne()JavaScript medium
1060 accepted
125. implement classNames()JavaScript medium
1048 accepted
103. implement Math.sqrt()JavaScript Algorithm medium
1046 accepted
131. implement _.chunk()JavaScript Lodash medium
1019 accepted
138. Intersection of two sorted arrays JavaScript Algorithm easy
1017 accepted
107. Find the largest difference JavaScript Algorithm easy
1016 accepted
38. implement `jest.spyOn()`JavaScript easy
1000 accepted
130. create LazyMan()JavaScript medium
992 accepted
69. implement deep equal `_.isEqual()`JavaScript Lodash medium
972 accepted
140. Virtual DOM III - Functional Component JavaScript easy
967 accepted
121. A number sequence JavaScript easy
949 accepted
105. find the first duplicate character in a string JavaScript string easy
948 accepted
85. implement `_.get()`JavaScript Lodash medium
939 accepted
97. compress a string JavaScript string easy
938 accepted
120. create `isPrime()`JavaScript Algorithm easy
930 accepted
106. Find two numbers that sum up to 0 JavaScript Algorithm easy
916 accepted
66. remove duplicates from an array JavaScript Algorithm medium
897 accepted
48. search first index with Binary Search(possible duplicate array)JavaScript Algorithm easy
872 accepted
81. merge sorted arrays JavaScript Algorithm easy
868 accepted
152. Find Top k Elements JavaScript Algorithm medium
867 accepted
156. implement `_.set()`JavaScript Lodash medium
865 accepted
54. flatten Thunk JavaScript easy
856 accepted
36. create a fake timer(setTimeout)JavaScript medium
856 accepted
86. Generate Fibonacci Number JavaScript Algorithm easy
837 accepted
102. validate string of parentheses JavaScript Algorithm string easy
818 accepted
55. highlight keywords in HTML string JavaScript Algorithm medium
815 accepted
116. implement Object.is()JavaScript easy
800 accepted
65. add comma to number JavaScript medium
777 accepted
90. write your own `instanceof`JavaScript medium
775 accepted
24. create a Priority Queue in JavaScript JavaScript Algorithm medium
768 accepted
109. implement `Math.pow()`JavaScript Algorithm easy
765 accepted
49. search last index with Binary Search(possible duplicate array)JavaScript Algorithm easy
758 accepted
59. create a browser history JavaScript medium
754 accepted
22. implement JSON.parse()JavaScript medium
742 accepted
93. Generate Fibonacci Number with recursion JavaScript easy
728 accepted
87. longest substring with unique characters JavaScript Algorithm easy
723 accepted
100. detect circle in linked list JavaScript Algorithm easy
719 accepted
135. localStorage with expiration JavaScript medium
716 accepted
27. implement completeAssign() JavaScript easy
699 accepted
139. implement _.partial()JavaScript Lodash medium
696 accepted
43. implement Quick Sort JavaScript Algorithm medium
679 accepted
101. merge identical API calls JavaScript medium
674 accepted
83. create an interval JavaScript medium
671 accepted
147. Pick up stones JavaScript easy
665 accepted
79. convert snake_case to camelCase JavaScript medium
665 accepted
42. implement Insertion Sort JavaScript Algorithm easy
665 accepted
52. create a middleware system JavaScript medium
657 accepted
95. implement String.prototype.trim()JavaScript medium
644 accepted
149. interpolation JavaScript medium
610 accepted
117. event delegation JavaScript medium
599 accepted
41. implement Merge Sort JavaScript Algorithm medium
598 accepted
44. implement Selection Sort JavaScript Algorithm easy
580 accepted
82. find available meeting slots JavaScript Algorithm medium
579 accepted
88. support negative Array index in JavaScript JavaScript medium
578 accepted
50. search element right before target with Binary Search(possible duplicate array)JavaScript Algorithm easy
578 accepted
170. Generate CSS Selector for target element JavaScript medium
560 accepted
51. search element right after target with Binary Search(possible duplicate array)JavaScript Algorithm easy
543 accepted
132. the angle between hour hand and minute hand of a clock JavaScript medium
533 accepted
136. find median of two sorted array JavaScript Algorithm medium
527 accepted
96. count "1" in binary form JavaScript easy
519 accepted
45. find the K-th largest element in an unsorted array JavaScript Algorithm medium
503 accepted
62. implement BigInt addition JavaScript Algorithm easy
498 accepted
111. Count palindromic substrings JavaScript Algorithm string easy
493 accepted
166. validate number string JavaScript Algorithm string medium
479 accepted
108. Implement a Stack by using Queue JavaScript Algorithm medium
473 accepted
153. uglify CSS class names JavaScript medium
466 accepted
112. remove duplicate characters in a string JavaScript Algorithm string medium
456 accepted
119. create a tokenizer JavaScript medium
446 accepted
80. implement your own URLSearchParams JavaScript hard?
422 accepted
70. implement Observable.from()JavaScript medium
404 accepted
142. lit-html 1 - tagged templates JavaScript lit-html easy
395 accepted
173. uncompress string JavaScript string algorithm medium
391 accepted
84. create a fake timer (setInterval)JavaScript medium
377 accepted
137. binary tree vertical traversal JavaScript Algorithm hard?
371 accepted
99. extract all anchor element from HTML string JavaScript medium
371 accepted
134. create your own Cookie JavaScript medium
356 accepted
172. implement `Math.clz32()`JavaScript medium
349 accepted
71. implement Observable Subject JavaScript medium
336 accepted
72. implement Observable interval()JavaScript easy
312 accepted
164. implement Immer produce()JavaScript medium
300 accepted
73. implement Observable fromEvent()JavaScript easy
275 accepted
98. validate an IP address JavaScript medium
273 accepted
74. implement Observable Transformation Operators JavaScript easy
273 accepted
75. implement BigInt subtraction JavaScript Algorithm medium
268 accepted
171. create callback on message channel JavaScript medium
230 accepted
78. convert HEX color to RGBA JavaScript medium
215 accepted
143. Virtual DOM IV - JSX 1 JavaScript medium
192 accepted
169. LRU - Chrome storage automatic eviction JavaScript Algorithm medium
185 accepted
141. implement btoa()JavaScript easy
164 accepted
124. calculate arithmetic expression JavaScript Algorithm medium
150 accepted
160. implement atob()JavaScript medium
129 accepted
76. implement BigInt addition with sign JavaScript medium
121 accepted
144. serialize and deserialize data types not supported in JSON JavaScript medium
108 accepted
150. Virtual DOM V - JSX 2 JavaScript medium
96 accepted
114. implement BigInt multiplication JavaScript medium
91 accepted
77. implement BigInt subtraction with sign JavaScript easy
64 accepted
126. BigDecimal addition JavaScript Algorithm medium
39 accepted
115. implement BigInt division JavaScript medium
38 accepted
128. BigDecimal multiplication JavaScript Algorithm medium
18 accepted
129. BigDecimal Division JavaScript Algorithm few challengers
16 accepted
127. BigDecimal subtraction JavaScript Algorithm few challengers
12 accepted
174. CSS Grid Layout auto-placement algorithm - sparse JavaScript CSS few challengers
3 accepted
175. CSS Grid Layout auto-placement algorithm - dense JavaScript CSS few challengers
2 accepted