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JavaScript Coding Questions
As a Front-End developer, JavaScript is the core skill of everything
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Difficulty
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Sort: most tried
tag: JavaScript
1. implement curry()
JavaScript
easy
57667 tried
3. implement Array.prototype.flat()
JavaScript
easy
53613 tried
4. implement basic throttle()
JavaScript
Lodash
medium
51579 tried
16. create an Event Emitter
JavaScript
medium
31978 tried
2. implement curry() with placeholder support
JavaScript
medium
29745 tried
151. implement Array.prototype.map()
JavaScript
medium
27512 tried
5. implement throttle() with leading & trailing option
JavaScript
Lodash
medium
24942 tried
6. implement basic debounce()
JavaScript
Lodash
easy
24114 tried
19. find corresponding node in two identical DOM tree
JavaScript
easy
22908 tried
14. Implement a general memoization function - `memo()`
JavaScript
medium
22081 tried
32. implement `Promise.all()`
JavaScript
medium
20921 tried
7. implement debounce() with leading & trailing option
JavaScript
Lodash
medium
20168 tried
113. Virtual DOM I
JavaScript
Algorithm
DOM
medium
18527 tried
9. decode message
JavaScript
medium
16932 tried
21. implement JSON.stringify()
JavaScript
medium
16590 tried
8. can you shuffle() an array?
JavaScript
medium
16536 tried
18. Improve a function
JavaScript
easy
15990 tried
176. undefined to null
JavaScript
easy
15155 tried
10. first bad version
JavaScript
Algorithm
medium
15110 tried
58. get DOM tree height
JavaScript
Algorithm
DOM
medium
15108 tried
26. implement Object.assign()
JavaScript
medium
14774 tried
34. implement `Promise.any()`
JavaScript
medium
14696 tried
146. implement Array.prototype.reduce()
JavaScript
medium
14286 tried
67. create your own Promise
JavaScript
medium
14127 tried
11. what is Composition? create a pipe()
JavaScript
easy
13952 tried
23. create a sum()
JavaScript
easy
13882 tried
161. toBe() or not.toBe()
JavaScript
medium
13514 tried
17. Create a simple store for DOM element
JavaScript
easy
13491 tried
28. implement clearAllTimeout()
JavaScript
easy
13160 tried
33. implement `Promise.allSettled()`
JavaScript
medium
12845 tried
92. throttle Promises
JavaScript
medium
12131 tried
57. create an Observable
JavaScript
medium
11934 tried
29. implement async helper - `sequence()`
JavaScript
medium
11787 tried
25. Reorder array with new indexes
JavaScript
Algorithm
easy
11326 tried
167. Intersection of unsorted arrays
JavaScript
Algorithm
easy
10830 tried
13. Implement a Queue by using Stack
JavaScript
Algorithm
medium
10439 tried
64. auto-retry Promise on rejection
JavaScript
medium
10368 tried
63. create `_.cloneDeep()`
JavaScript
Algorithm
Lodash
medium
10329 tried
15. implement a simple DOM wrapper to support method chaining like jQuery
JavaScript
easy
10312 tried
159. implement promisify()
JavaScript
medium
10293 tried
130. create LazyMan()
JavaScript
medium
9621 tried
12. implement Immutability helper
JavaScript
medium
9613 tried
155. create a count function
JavaScript
easy
9422 tried
162. find the single integer
JavaScript
Algorithm
easy
9302 tried
30. implement async helper - `parallel()`
JavaScript
medium
8985 tried
68. get DOM tags
JavaScript
Algorithm
DOM
medium
8392 tried
110. serialize and deserialize binary tree
JavaScript
Algorithm
medium
8268 tried
104. Traverse DOM level by level
JavaScript
Algorithm
DOM
easy
8219 tried
154. Two-way binding
JavaScript
DOM
easy
7462 tried
148. create a counter object
JavaScript
easy
7394 tried
103. implement Math.sqrt()
JavaScript
Algorithm
medium
7366 tried
168. move zeros
JavaScript
Algorithm
medium
7050 tried
122. implement memoizeOne()
JavaScript
medium
6964 tried
20. Detect data type in JavaScript
JavaScript
medium
6937 tried
56. call APIs with pagination
JavaScript
medium
6883 tried
123. implement Promise.prototype.finally()
JavaScript
medium
6801 tried
89. Next Right Sibling
JavaScript
DOM
easy
6776 tried
53. write your own `extends` in es5
JavaScript
medium
6490 tried
157. semver compare
JavaScript
easy
6013 tried
135. localStorage with expiration
JavaScript
medium
5948 tried
61. create your own `Function.prototype.call`
JavaScript
medium
5927 tried
69. implement deep equal `_.isEqual()`
JavaScript
Lodash
medium
5898 tried
125. implement classNames()
JavaScript
medium
5635 tried
46. implement `_.once()`
JavaScript
Lodash
medium
5609 tried
60. create your own `new` operator
JavaScript
easy
5604 tried
91. invert a binary tree
JavaScript
Algorithm
easy
5602 tried
158. Previous Left Sibling
JavaScript
DOM
medium
5553 tried
36. create a fake timer(setTimeout)
JavaScript
medium
5540 tried
80. implement your own URLSearchParams
JavaScript
hard?
5315 tried
101. merge identical API calls
JavaScript
medium
5284 tried
35. implement `Promise.race()`
JavaScript
easy
5242 tried
85. implement `_.get()`
JavaScript
Lodash
medium
5126 tried
47. reverse a linked list
JavaScript
Algorithm
easy
5079 tried
22. implement JSON.parse()
JavaScript
medium
5024 tried
137. binary tree vertical traversal
JavaScript
Algorithm
hard?
5003 tried
173. uncompress string
JavaScript
string
algorithm
medium
5000 tried
59. create a browser history
JavaScript
medium
4962 tried
37. implement Binary Search (unique)
JavaScript
easy
4937 tried
118. Virtual DOM II - createElement
JavaScript
easy
4793 tried
156. implement `_.set()`
JavaScript
Lodash
medium
4781 tried
145. most frequently occurring character
JavaScript
easy
4753 tried
39. implement range()
JavaScript
easy
4651 tried
163. integer to roman numerals
JavaScript
Algorithm
easy
4524 tried
117. event delegation
JavaScript
medium
4484 tried
31. implement async helper - `race()`
JavaScript
easy
4430 tried
131. implement _.chunk()
JavaScript
Lodash
medium
4288 tried
83. create an interval
JavaScript
medium
4288 tried
24. create a Priority Queue in JavaScript
JavaScript
Algorithm
medium
4276 tried
66. remove duplicates from an array
JavaScript
Algorithm
medium
4178 tried
121. A number sequence
JavaScript
easy
4166 tried
52. create a middleware system
JavaScript
medium
4090 tried
139. implement _.partial()
JavaScript
Lodash
medium
4079 tried
134. create your own Cookie
JavaScript
medium
4029 tried
120. create `isPrime()`
JavaScript
Algorithm
easy
3965 tried
112. remove duplicate characters in a string
JavaScript
Algorithm
string
medium
3930 tried
152. Find Top k Elements
JavaScript
Algorithm
medium
3919 tried
86. Generate Fibonacci Number
JavaScript
Algorithm
medium
3917 tried
65. add comma to number
JavaScript
medium
3881 tried
97. compress a string
JavaScript
string
easy
3860 tried
138. Intersection of two sorted arrays
JavaScript
Algorithm
easy
3827 tried
38. implement `jest.spyOn()`
JavaScript
easy
3783 tried
140. Virtual DOM III - Functional Component
JavaScript
easy
3759 tried
133. roman numerals to integer
JavaScript
easy
3739 tried
95. implement String.prototype.trim()
JavaScript
medium
3690 tried
41. implement Merge Sort
JavaScript
Algorithm
medium
3668 tried
81. merge sorted arrays
JavaScript
Algorithm
easy
3640 tried
48. search first index with Binary Search(possible duplicate array)
JavaScript
Algorithm
easy
3599 tried
88. support negative Array index in JavaScript
JavaScript
medium
3593 tried
94. implement your own `Object.create`
JavaScript
easy
3576 tried
149. interpolation
JavaScript
medium
3510 tried
90. write your own `instanceof`
JavaScript
medium
3479 tried
132. the angle between hour hand and minute hand of a clock
JavaScript
medium
3445 tried
166. validate number string
JavaScript
Algorithm
string
medium
3427 tried
170. Generate CSS Selector for target element
JavaScript
medium
3425 tried
87. longest substring with unique characters
JavaScript
Algorithm
easy
3420 tried
43. implement Quick Sort
JavaScript
Algorithm
medium
3410 tried
55. highlight keywords in HTML string
JavaScript
Algorithm
medium
3383 tried
116. implement Object.is()
JavaScript
easy
3330 tried
79. convert snake_case to camelCase
JavaScript
medium
3288 tried
102. validate string of parentheses
JavaScript
Algorithm
string
easy
3182 tried
106. Find two numbers that sum up to 0
JavaScript
Algorithm
easy
3153 tried
109. implement `Math.pow()`
JavaScript
Algorithm
easy
3144 tried
70. implement Observable.from()
JavaScript
medium
3102 tried
27. implement completeAssign()
JavaScript
medium
3099 tried
40. implement Bubble Sort
JavaScript
Algorithm
easy
3064 tried
147. Pick up stones
JavaScript
easy
3002 tried
136. find median of two sorted array
JavaScript
Algorithm
medium
2962 tried
54. flatten Thunk
JavaScript
easy
2919 tried
153. uglify CSS class names
JavaScript
medium
2836 tried
107. Find the largest difference
JavaScript
Algorithm
easy
2822 tried
49. search last index with Binary Search(possible duplicate array)
JavaScript
Algorithm
easy
2743 tried
169. LRU - Chrome storage automatic eviction
JavaScript
Algorithm
medium
2723 tried
105. find the first duplicate character in a string
JavaScript
string
easy
2633 tried
82. find available meeting slots
JavaScript
Algorithm
medium
2620 tried
164. implement Immer produce()
JavaScript
medium
2579 tried
100. detect circle in linked list
JavaScript
Algorithm
easy
2512 tried
45. find the K-th largest element in an unsorted array
JavaScript
Algorithm
medium
2399 tried
172. implement `Math.clz32()`
JavaScript
medium
2314 tried
71. implement Observable Subject
JavaScript
medium
2115 tried
108. Implement a Stack by using Queue
JavaScript
Algorithm
medium
2073 tried
50. search element right before target with Binary Search(possible duplicate array)
JavaScript
Algorithm
easy
2069 tried
111. Count palindromic substrings
JavaScript
Algorithm
string
easy
2064 tried
93. Generate Fibonacci Number with recursion
JavaScript
easy
2030 tried
119. create a tokenizer
JavaScript
medium
2026 tried
62. implement BigInt addition
JavaScript
Algorithm
easy
1949 tried
99. extract all anchor element from HTML string
JavaScript
medium
1924 tried
51. search element right after target with Binary Search(possible duplicate array)
JavaScript
Algorithm
easy
1890 tried
84. create a fake timer (setInterval)
JavaScript
medium
1780 tried
171. create callback on message channel
JavaScript
medium
1768 tried
143. Virtual DOM IV - JSX 1
JavaScript
medium
1765 tried
42. implement Insertion Sort
JavaScript
Algorithm
easy
1732 tried
98. validate an IP address
JavaScript
medium
1713 tried
44. implement Selection Sort
JavaScript
Algorithm
easy
1573 tried
78. convert HEX color to RGBA
JavaScript
medium
1436 tried
142. lit-html 1 - tagged templates
JavaScript
lit-html
easy
1421 tried
75. implement BigInt subtraction
JavaScript
Algorithm
medium
1252 tried
96. count "1" in binary form
JavaScript
easy
1191 tried
150. Virtual DOM V - JSX 2
JavaScript
medium
963 tried
160. implement atob()
JavaScript
medium
844 tried
144. serialize and deserialize data types not supported in JSON
JavaScript
medium
809 tried
76. implement BigInt addition with sign
JavaScript
medium
785 tried
73. implement Observable fromEvent()
JavaScript
easy
780 tried
124. calculate arithmetic expression
JavaScript
Algorithm
medium
720 tried
74. implement Observable Transformation Operators
JavaScript
easy
643 tried
141. implement btoa()
JavaScript
easy
601 tried
72. implement Observable interval()
JavaScript
easy
556 tried
174. CSS Grid Layout auto-placement algorithm - sparse
JavaScript
CSS
hard?
493 tried
114. implement BigInt multiplication
JavaScript
medium
446 tried
77. implement BigInt subtraction with sign
JavaScript
medium
349 tried
126. BigDecimal addition
JavaScript
Algorithm
medium
270 tried
115. implement BigInt division
JavaScript
medium
251 tried
128. BigDecimal multiplication
JavaScript
Algorithm
medium
196 tried
129. BigDecimal Division
JavaScript
Algorithm
medium
138 tried
175. CSS Grid Layout auto-placement algorithm - dense
JavaScript
CSS
few challengers
94 tried
127. BigDecimal subtraction
JavaScript
Algorithm
few challengers
83 tried