BFE
.dev
buy us
a coffee
EN
Practice
Explore
EN
JavaScript Coding Questions
As a Front-End developer, JavaScript is the core skill of everything
Sort
Difficulty
Solved status
Company
Sort: most accepted
Difficulty: medium
tag: JavaScript
4. implement basic throttle()
JavaScript
Lodash
medium
12862 accepted
16. create an Event Emitter
JavaScript
medium
8239 accepted
2. implement curry() with placeholder support
JavaScript
medium
6457 accepted
14. Implement a general memoization function - `memo()`
JavaScript
medium
6162 accepted
32. implement `Promise.all()`
JavaScript
medium
5877 accepted
8. can you shuffle() an array?
JavaScript
medium
5061 accepted
9. decode message
JavaScript
medium
4601 accepted
7. implement debounce() with leading & trailing option
JavaScript
Lodash
medium
4584 accepted
10. first bad version
JavaScript
Algorithm
medium
4570 accepted
58. get DOM tree height
JavaScript
Algorithm
DOM
medium
4564 accepted
5. implement throttle() with leading & trailing option
JavaScript
Lodash
medium
4423 accepted
151. implement Array.prototype.map()
JavaScript
medium
4182 accepted
33. implement `Promise.allSettled()`
JavaScript
medium
3183 accepted
29. implement async helper - `sequence()`
JavaScript
medium
3139 accepted
113. Virtual DOM I
JavaScript
Algorithm
DOM
medium
3092 accepted
34. implement `Promise.any()`
JavaScript
medium
3070 accepted
161. toBe() or not.toBe()
JavaScript
medium
2784 accepted
92. throttle Promises
JavaScript
medium
2697 accepted
64. auto-retry Promise on rejection
JavaScript
medium
2640 accepted
13. Implement a Queue by using Stack
JavaScript
Algorithm
medium
2553 accepted
68. get DOM tags
JavaScript
Algorithm
DOM
medium
2528 accepted
104. Traverse DOM level by level
JavaScript
Algorithm
DOM
medium
2524 accepted
57. create an Observable
JavaScript
medium
2471 accepted
146. implement Array.prototype.reduce()
JavaScript
medium
2347 accepted
67. create your own Promise
JavaScript
medium
2123 accepted
26. implement Object.assign()
JavaScript
medium
2112 accepted
110. serialize and deserialize binary tree
JavaScript
Algorithm
medium
2074 accepted
12. implement Immutability helper
JavaScript
medium
2018 accepted
30. implement async helper - `parallel()`
JavaScript
medium
2015 accepted
168. move zeros
JavaScript
Algorithm
medium
1999 accepted
20. Detect data type in JavaScript
JavaScript
medium
1995 accepted
63. create `_.cloneDeep()`
JavaScript
Algorithm
Lodash
medium
1813 accepted
21. implement JSON.stringify()
JavaScript
medium
1770 accepted
56. call APIs with pagination
JavaScript
medium
1702 accepted
123. implement Promise.prototype.finally()
JavaScript
medium
1592 accepted
61. create your own `Function.prototype.call`
JavaScript
medium
1583 accepted
103. implement Math.sqrt()
JavaScript
Algorithm
medium
1542 accepted
158. Previous Left Sibling
JavaScript
DOM
medium
1490 accepted
85. implement `_.get()`
JavaScript
Lodash
medium
1468 accepted
125. implement classNames()
JavaScript
medium
1445 accepted
53. write your own `extends` in es5
JavaScript
medium
1347 accepted
69. implement deep equal `_.isEqual()`
JavaScript
Lodash
medium
1340 accepted
131. implement _.chunk()
JavaScript
Lodash
medium
1288 accepted
130. create LazyMan()
JavaScript
medium
1278 accepted
122. implement memoizeOne()
JavaScript
medium
1271 accepted
86. Generate Fibonacci Number
JavaScript
Algorithm
medium
1187 accepted
83. create an interval
JavaScript
medium
1163 accepted
66. remove duplicates from an array
JavaScript
Algorithm
medium
1149 accepted
173. uncompress string
JavaScript
string
algorithm
medium
1142 accepted
36. create a fake timer(setTimeout)
JavaScript
medium
1084 accepted
152. Find Top k Elements
JavaScript
Algorithm
medium
1081 accepted
156. implement `_.set()`
JavaScript
Lodash
medium
1079 accepted
90. write your own `instanceof`
JavaScript
medium
1022 accepted
24. create a Priority Queue in JavaScript
JavaScript
Algorithm
medium
1009 accepted
65. add comma to number
JavaScript
medium
1004 accepted
55. highlight keywords in HTML string
JavaScript
Algorithm
medium
1000 accepted
22. implement JSON.parse()
JavaScript
medium
987 accepted
59. create a browser history
JavaScript
medium
963 accepted
27. implement completeAssign()
JavaScript
medium
933 accepted
135. localStorage with expiration
JavaScript
medium
914 accepted
43. implement Quick Sort
JavaScript
Algorithm
medium
896 accepted
101. merge identical API calls
JavaScript
medium
888 accepted
139. implement _.partial()
JavaScript
Lodash
medium
879 accepted
52. create a middleware system
JavaScript
medium
853 accepted
79. convert snake_case to camelCase
JavaScript
medium
830 accepted
95. implement String.prototype.trim()
JavaScript
medium
821 accepted
170. Generate CSS Selector for target element
JavaScript
medium
809 accepted
41. implement Merge Sort
JavaScript
Algorithm
medium
805 accepted
82. find available meeting slots
JavaScript
Algorithm
medium
777 accepted
88. support negative Array index in JavaScript
JavaScript
medium
735 accepted
166. validate number string
JavaScript
Algorithm
string
medium
728 accepted
117. event delegation
JavaScript
medium
723 accepted
149. interpolation
JavaScript
medium
714 accepted
136. find median of two sorted array
JavaScript
Algorithm
medium
696 accepted
45. find the K-th largest element in an unsorted array
JavaScript
Algorithm
medium
669 accepted
111. Count palindromic substrings
JavaScript
Algorithm
string
medium
633 accepted
132. the angle between hour hand and minute hand of a clock
JavaScript
medium
627 accepted
108. Implement a Stack by using Queue
JavaScript
Algorithm
medium
601 accepted
119. create a tokenizer
JavaScript
medium
553 accepted
153. uglify CSS class names
JavaScript
medium
541 accepted
112. remove duplicate characters in a string
JavaScript
Algorithm
string
medium
532 accepted
172. implement `Math.clz32()`
JavaScript
medium
508 accepted
70. implement Observable.from()
JavaScript
medium
506 accepted
134. create your own Cookie
JavaScript
medium
470 accepted
84. create a fake timer (setInterval)
JavaScript
medium
467 accepted
71. implement Observable Subject
JavaScript
medium
442 accepted
99. extract all anchor element from HTML string
JavaScript
medium
431 accepted
171. create callback on message channel
JavaScript
medium
400 accepted
164. implement Immer produce()
JavaScript
medium
395 accepted
75. implement BigInt subtraction
JavaScript
Algorithm
medium
370 accepted
98. validate an IP address
JavaScript
medium
336 accepted
169. LRU - Chrome storage automatic eviction
JavaScript
Algorithm
medium
308 accepted
78. convert HEX color to RGBA
JavaScript
medium
290 accepted
143. Virtual DOM IV - JSX 1
JavaScript
medium
265 accepted
124. calculate arithmetic expression
JavaScript
Algorithm
medium
195 accepted
76. implement BigInt addition with sign
JavaScript
medium
176 accepted
160. implement atob()
JavaScript
medium
167 accepted
144. serialize and deserialize data types not supported in JSON
JavaScript
medium
145 accepted
114. implement BigInt multiplication
JavaScript
medium
130 accepted
150. Virtual DOM V - JSX 2
JavaScript
medium
129 accepted
77. implement BigInt subtraction with sign
JavaScript
medium
103 accepted
115. implement BigInt division
JavaScript
medium
61 accepted
126. BigDecimal addition
JavaScript
Algorithm
medium
54 accepted
129. BigDecimal Division
JavaScript
Algorithm
medium
34 accepted
128. BigDecimal multiplication
JavaScript
Algorithm
medium
33 accepted
175. CSS Grid Layout auto-placement algorithm - dense
JavaScript
CSS
medium
13 accepted