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JavaScript Coding Questions
As a Front-End developer, JavaScript is the core skill of everything
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Sort: most tried
tag: JavaScript
1. implement curry()
JavaScript
easy
58730 tried
3. implement Array.prototype.flat()
JavaScript
easy
54438 tried
4. implement basic throttle()
JavaScript
Lodash
medium
52492 tried
16. create an Event Emitter
JavaScript
medium
32373 tried
2. implement curry() with placeholder support
JavaScript
medium
30290 tried
151. implement Array.prototype.map()
JavaScript
medium
27755 tried
5. implement throttle() with leading & trailing option
JavaScript
Lodash
medium
25418 tried
6. implement basic debounce()
JavaScript
Lodash
easy
24574 tried
19. find corresponding node in two identical DOM tree
JavaScript
easy
23081 tried
14. Implement a general memoization function - `memo()`
JavaScript
medium
22425 tried
32. implement `Promise.all()`
JavaScript
medium
21451 tried
7. implement debounce() with leading & trailing option
JavaScript
Lodash
medium
20639 tried
113. Virtual DOM I
JavaScript
Algorithm
DOM
medium
18717 tried
9. decode message
JavaScript
medium
17294 tried
21. implement JSON.stringify()
JavaScript
medium
16908 tried
8. can you shuffle() an array?
JavaScript
medium
16787 tried
18. Improve a function
JavaScript
easy
16212 tried
176. undefined to null
JavaScript
easy
16010 tried
10. first bad version
JavaScript
Algorithm
medium
15365 tried
58. get DOM tree height
JavaScript
Algorithm
DOM
medium
15313 tried
34. implement `Promise.any()`
JavaScript
medium
15083 tried
26. implement Object.assign()
JavaScript
medium
14996 tried
146. implement Array.prototype.reduce()
JavaScript
medium
14398 tried
67. create your own Promise
JavaScript
medium
14330 tried
11. what is Composition? create a pipe()
JavaScript
easy
14252 tried
23. create a sum()
JavaScript
easy
14092 tried
161. toBe() or not.toBe()
JavaScript
medium
13666 tried
17. Create a simple store for DOM element
JavaScript
easy
13629 tried
28. implement clearAllTimeout()
JavaScript
easy
13268 tried
33. implement `Promise.allSettled()`
JavaScript
medium
13100 tried
92. throttle Promises
JavaScript
medium
12299 tried
57. create an Observable
JavaScript
medium
12072 tried
29. implement async helper - `sequence()`
JavaScript
medium
12044 tried
25. Reorder array with new indexes
JavaScript
Algorithm
easy
11485 tried
167. Intersection of unsorted arrays
JavaScript
Algorithm
easy
11187 tried
13. Implement a Queue by using Stack
JavaScript
Algorithm
medium
10662 tried
64. auto-retry Promise on rejection
JavaScript
medium
10616 tried
159. implement promisify()
JavaScript
easy
10612 tried
63. create `_.cloneDeep()`
JavaScript
Algorithm
Lodash
medium
10528 tried
15. implement a simple DOM wrapper to support method chaining like jQuery
JavaScript
easy
10421 tried
12. implement Immutability helper
JavaScript
medium
9763 tried
130. create LazyMan()
JavaScript
medium
9707 tried
155. create a count function
JavaScript
easy
9559 tried
162. find the single integer
JavaScript
Algorithm
easy
9451 tried
30. implement async helper - `parallel()`
JavaScript
medium
9220 tried
68. get DOM tags
JavaScript
Algorithm
DOM
medium
8465 tried
104. Traverse DOM level by level
JavaScript
Algorithm
DOM
medium
8382 tried
110. serialize and deserialize binary tree
JavaScript
Algorithm
medium
8344 tried
154. Two-way binding
JavaScript
DOM
easy
7576 tried
103. implement Math.sqrt()
JavaScript
Algorithm
medium
7507 tried
148. create a counter object
JavaScript
easy
7502 tried
168. move zeros
JavaScript
Algorithm
medium
7156 tried
20. Detect data type in JavaScript
JavaScript
medium
7081 tried
56. call APIs with pagination
JavaScript
medium
7070 tried
122. implement memoizeOne()
JavaScript
medium
7030 tried
89. Next Right Sibling
JavaScript
DOM
easy
6863 tried
123. implement Promise.prototype.finally()
JavaScript
medium
6825 tried
53. write your own `extends` in es5
JavaScript
medium
6645 tried
157. semver compare
JavaScript
easy
6103 tried
61. create your own `Function.prototype.call`
JavaScript
medium
6022 tried
135. localStorage with expiration
JavaScript
medium
5993 tried
69. implement deep equal `_.isEqual()`
JavaScript
Lodash
medium
5983 tried
46. implement `_.once()`
JavaScript
Lodash
easy
5911 tried
125. implement classNames()
JavaScript
medium
5743 tried
60. create your own `new` operator
JavaScript
easy
5672 tried
91. invert a binary tree
JavaScript
Algorithm
easy
5648 tried
36. create a fake timer(setTimeout)
JavaScript
medium
5642 tried
158. Previous Left Sibling
JavaScript
DOM
medium
5621 tried
80. implement your own URLSearchParams
JavaScript
hard?
5397 tried
35. implement `Promise.race()`
JavaScript
easy
5345 tried
101. merge identical API calls
JavaScript
medium
5306 tried
85. implement `_.get()`
JavaScript
Lodash
medium
5209 tried
47. reverse a linked list
JavaScript
Algorithm
easy
5174 tried
173. uncompress string
JavaScript
string
algorithm
medium
5111 tried
22. implement JSON.parse()
JavaScript
medium
5073 tried
137. binary tree vertical traversal
JavaScript
Algorithm
hard?
5046 tried
59. create a browser history
JavaScript
medium
5041 tried
37. implement Binary Search (unique)
JavaScript
easy
5020 tried
156. implement `_.set()`
JavaScript
Lodash
medium
4848 tried
118. Virtual DOM II - createElement
JavaScript
easy
4838 tried
145. most frequently occurring character
JavaScript
easy
4820 tried
39. implement range()
JavaScript
easy
4711 tried
163. integer to roman numerals
JavaScript
Algorithm
easy
4592 tried
117. event delegation
JavaScript
medium
4527 tried
31. implement async helper - `race()`
JavaScript
easy
4522 tried
83. create an interval
JavaScript
medium
4389 tried
24. create a Priority Queue in JavaScript
JavaScript
Algorithm
medium
4372 tried
131. implement _.chunk()
JavaScript
Lodash
medium
4341 tried
66. remove duplicates from an array
JavaScript
Algorithm
medium
4223 tried
121. A number sequence
JavaScript
easy
4213 tried
52. create a middleware system
JavaScript
medium
4208 tried
139. implement _.partial()
JavaScript
Lodash
medium
4094 tried
134. create your own Cookie
JavaScript
medium
4039 tried
120. create `isPrime()`
JavaScript
Algorithm
easy
4004 tried
152. Find Top k Elements
JavaScript
Algorithm
medium
3965 tried
86. Generate Fibonacci Number
JavaScript
Algorithm
medium
3958 tried
112. remove duplicate characters in a string
JavaScript
Algorithm
string
medium
3948 tried
65. add comma to number
JavaScript
medium
3933 tried
97. compress a string
JavaScript
string
easy
3899 tried
138. Intersection of two sorted arrays
JavaScript
Algorithm
easy
3862 tried
38. implement `jest.spyOn()`
JavaScript
easy
3854 tried
133. roman numerals to integer
JavaScript
easy
3825 tried
140. Virtual DOM III - Functional Component
JavaScript
easy
3787 tried
41. implement Merge Sort
JavaScript
Algorithm
medium
3716 tried
81. merge sorted arrays
JavaScript
Algorithm
easy
3702 tried
95. implement String.prototype.trim()
JavaScript
medium
3700 tried
48. search first index with Binary Search(possible duplicate array)
JavaScript
Algorithm
easy
3678 tried
88. support negative Array index in JavaScript
JavaScript
medium
3647 tried
94. implement your own `Object.create`
JavaScript
easy
3626 tried
149. interpolation
JavaScript
medium
3538 tried
90. write your own `instanceof`
JavaScript
medium
3516 tried
166. validate number string
JavaScript
Algorithm
string
medium
3506 tried
43. implement Quick Sort
JavaScript
Algorithm
medium
3482 tried
170. Generate CSS Selector for target element
JavaScript
medium
3470 tried
87. longest substring with unique characters
JavaScript
Algorithm
easy
3460 tried
55. highlight keywords in HTML string
JavaScript
Algorithm
medium
3450 tried
132. the angle between hour hand and minute hand of a clock
JavaScript
medium
3449 tried
116. implement Object.is()
JavaScript
easy
3408 tried
79. convert snake_case to camelCase
JavaScript
medium
3314 tried
102. validate string of parentheses
JavaScript
Algorithm
string
easy
3217 tried
106. Find two numbers that sum up to 0
JavaScript
Algorithm
easy
3198 tried
109. implement `Math.pow()`
JavaScript
Algorithm
easy
3179 tried
27. implement completeAssign()
JavaScript
medium
3141 tried
40. implement Bubble Sort
JavaScript
Algorithm
easy
3114 tried
70. implement Observable.from()
JavaScript
medium
3105 tried
147. Pick up stones
JavaScript
easy
3059 tried
54. flatten Thunk
JavaScript
easy
3019 tried
136. find median of two sorted array
JavaScript
Algorithm
medium
2993 tried
107. Find the largest difference
JavaScript
Algorithm
easy
2945 tried
153. uglify CSS class names
JavaScript
medium
2865 tried
169. LRU - Chrome storage automatic eviction
JavaScript
Algorithm
medium
2808 tried
49. search last index with Binary Search(possible duplicate array)
JavaScript
Algorithm
easy
2793 tried
105. find the first duplicate character in a string
JavaScript
string
easy
2683 tried
82. find available meeting slots
JavaScript
Algorithm
medium
2632 tried
164. implement Immer produce()
JavaScript
medium
2589 tried
100. detect circle in linked list
JavaScript
Algorithm
easy
2545 tried
45. find the K-th largest element in an unsorted array
JavaScript
Algorithm
medium
2442 tried
172. implement `Math.clz32()`
JavaScript
medium
2365 tried
50. search element right before target with Binary Search(possible duplicate array)
JavaScript
Algorithm
easy
2175 tried
71. implement Observable Subject
JavaScript
medium
2116 tried
111. Count palindromic substrings
JavaScript
Algorithm
string
medium
2101 tried
108. Implement a Stack by using Queue
JavaScript
Algorithm
medium
2093 tried
93. Generate Fibonacci Number with recursion
JavaScript
easy
2049 tried
119. create a tokenizer
JavaScript
medium
2042 tried
62. implement BigInt addition
JavaScript
Algorithm
easy
1969 tried
99. extract all anchor element from HTML string
JavaScript
medium
1933 tried
51. search element right after target with Binary Search(possible duplicate array)
JavaScript
Algorithm
easy
1927 tried
171. create callback on message channel
JavaScript
medium
1824 tried
84. create a fake timer (setInterval)
JavaScript
medium
1780 tried
143. Virtual DOM IV - JSX 1
JavaScript
medium
1769 tried
42. implement Insertion Sort
JavaScript
Algorithm
easy
1756 tried
98. validate an IP address
JavaScript
medium
1729 tried
44. implement Selection Sort
JavaScript
Algorithm
easy
1604 tried
142. lit-html 1 - tagged templates
JavaScript
lit-html
easy
1442 tried
78. convert HEX color to RGBA
JavaScript
medium
1442 tried
75. implement BigInt subtraction
JavaScript
Algorithm
medium
1252 tried
96. count "1" in binary form
JavaScript
easy
1208 tried
150. Virtual DOM V - JSX 2
JavaScript
medium
963 tried
160. implement atob()
JavaScript
medium
864 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
783 tried
124. calculate arithmetic expression
JavaScript
Algorithm
medium
721 tried
74. implement Observable Transformation Operators
JavaScript
easy
646 tried
141. implement btoa()
JavaScript
easy
606 tried
72. implement Observable interval()
JavaScript
easy
557 tried
174. CSS Grid Layout auto-placement algorithm - sparse
JavaScript
CSS
hard?
512 tried
114. implement BigInt multiplication
JavaScript
medium
447 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
medium
100 tried
127. BigDecimal subtraction
JavaScript
Algorithm
few challengers
83 tried