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 liked
Difficulty: medium
2. implement curry() with placeholder support
JavaScript
medium
52 likes
16. create an Event Emitter
JavaScript
medium
50 likes
4. implement basic throttle()
JavaScript
Lodash
medium
44 likes
113. Virtual DOM I
JavaScript
Algorithm
DOM
medium
41 likes
67. create your own Promise
JavaScript
medium
41 likes
130. create LazyMan()
JavaScript
medium
37 likes
10. first bad version
JavaScript
Algorithm
medium
34 likes
12. implement Immutability helper
JavaScript
medium
32 likes
29. implement async helper - `sequence()`
JavaScript
medium
31 likes
92. throttle Promises
JavaScript
medium
30 likes
57. create an Observable
JavaScript
medium
30 likes
64. auto-retry Promise on rejection
JavaScript
medium
29 likes
32. implement `Promise.all()`
JavaScript
medium
29 likes
14. Implement a general memoization function - `memo()`
JavaScript
medium
29 likes
151. implement Array.prototype.map()
JavaScript
medium
27 likes
58. get DOM tree height
JavaScript
Algorithm
DOM
medium
27 likes
21. implement JSON.stringify()
JavaScript
medium
26 likes
34. implement `Promise.any()`
JavaScript
medium
25 likes
146. implement Array.prototype.reduce()
JavaScript
medium
24 likes
165. remove characters
Algorithm
medium
23 likes
161. toBe() or not.toBe()
JavaScript
medium
23 likes
9. decode message
JavaScript
medium
23 likes
8. can you shuffle() an array?
JavaScript
medium
22 likes
5. implement throttle() with leading & trailing option
JavaScript
Lodash
medium
22 likes
61. create your own `Function.prototype.call`
JavaScript
medium
21 likes
55. highlight keywords in HTML string
JavaScript
Algorithm
medium
21 likes
13. Implement a Queue by using Stack
JavaScript
Algorithm
medium
21 likes
173. uncompress string
JavaScript
string
algorithm
medium
20 likes
63. create `_.cloneDeep()`
JavaScript
Algorithm
Lodash
medium
20 likes
7. implement debounce() with leading & trailing option
JavaScript
Lodash
medium
20 likes
168. move zeros
JavaScript
Algorithm
medium
19 likes
33. implement `Promise.allSettled()`
JavaScript
medium
18 likes
123. implement Promise.prototype.finally()
JavaScript
medium
17 likes
117. event delegation
JavaScript
medium
17 likes
104. Traverse DOM level by level
JavaScript
Algorithm
DOM
medium
17 likes
85. implement `_.get()`
JavaScript
Lodash
medium
17 likes
69. implement deep equal `_.isEqual()`
JavaScript
Lodash
medium
17 likes
68. get DOM tags
JavaScript
Algorithm
DOM
medium
16 likes
101. merge identical API calls
JavaScript
medium
15 likes
22. implement JSON.parse()
JavaScript
medium
15 likes
20. Detect data type in JavaScript
JavaScript
medium
15 likes
125. implement classNames()
JavaScript
medium
14 likes
110. serialize and deserialize binary tree
JavaScript
Algorithm
medium
14 likes
88. support negative Array index in JavaScript
JavaScript
medium
14 likes
30. implement async helper - `parallel()`
JavaScript
medium
14 likes
164. implement Immer produce()
JavaScript
medium
13 likes
83. create an interval
JavaScript
medium
13 likes
70. implement Observable.from()
JavaScript
medium
13 likes
56. call APIs with pagination
JavaScript
medium
13 likes
52. create a middleware system
JavaScript
medium
13 likes
36. create a fake timer(setTimeout)
JavaScript
medium
13 likes
26. implement Object.assign()
JavaScript
medium
13 likes
24. create a Priority Queue in JavaScript
JavaScript
Algorithm
medium
13 likes
158. Previous Left Sibling
JavaScript
DOM
medium
12 likes
139. implement _.partial()
JavaScript
Lodash
medium
12 likes
112. remove duplicate characters in a string
JavaScript
Algorithm
string
medium
12 likes
59. create a browser history
JavaScript
medium
12 likes
156. implement `_.set()`
JavaScript
Lodash
medium
11 likes
153. uglify CSS class names
JavaScript
medium
11 likes
122. implement memoizeOne()
JavaScript
medium
11 likes
82. find available meeting slots
JavaScript
Algorithm
medium
11 likes
79. convert snake_case to camelCase
JavaScript
medium
11 likes
65. add comma to number
JavaScript
medium
11 likes
149. interpolation
JavaScript
medium
10 likes
143. Virtual DOM IV - JSX 1
JavaScript
medium
10 likes
134. create your own Cookie
JavaScript
medium
10 likes
111. Count palindromic substrings
JavaScript
Algorithm
string
medium
10 likes
66. remove duplicates from an array
JavaScript
Algorithm
medium
10 likes
53. write your own `extends` in es5
JavaScript
medium
10 likes
45. find the K-th largest element in an unsorted array
JavaScript
Algorithm
medium
10 likes
152. Find Top k Elements
JavaScript
Algorithm
medium
9 likes
119. create a tokenizer
JavaScript
medium
9 likes
103. implement Math.sqrt()
JavaScript
Algorithm
medium
9 likes
90. write your own `instanceof`
JavaScript
medium
9 likes
135. localStorage with expiration
JavaScript
medium
8 likes
131. implement _.chunk()
JavaScript
Lodash
medium
8 likes
99. extract all anchor element from HTML string
JavaScript
medium
8 likes
43. implement Quick Sort
JavaScript
Algorithm
medium
8 likes
41. implement Merge Sort
JavaScript
Algorithm
medium
8 likes
108. Implement a Stack by using Queue
JavaScript
Algorithm
medium
7 likes
86. Generate Fibonacci Number
JavaScript
Algorithm
medium
7 likes
171. create callback on message channel
JavaScript
medium
6 likes
170. Generate CSS Selector for target element
JavaScript
medium
6 likes
169. LRU - Chrome storage automatic eviction
JavaScript
Algorithm
medium
6 likes
95. implement String.prototype.trim()
JavaScript
medium
6 likes
84. create a fake timer (setInterval)
JavaScript
medium
6 likes
78. convert HEX color to RGBA
JavaScript
medium
6 likes
27. implement completeAssign()
JavaScript
medium
6 likes
172. implement `Math.clz32()`
JavaScript
medium
5 likes
166. validate number string
JavaScript
Algorithm
string
medium
5 likes
75. implement BigInt subtraction
JavaScript
Algorithm
medium
5 likes
71. implement Observable Subject
JavaScript
medium
5 likes
160. implement atob()
JavaScript
medium
4 likes
144. serialize and deserialize data types not supported in JSON
JavaScript
medium
4 likes
136. find median of two sorted array
JavaScript
Algorithm
medium
4 likes
124. calculate arithmetic expression
JavaScript
Algorithm
medium
4 likes
98. validate an IP address
JavaScript
medium
4 likes
150. Virtual DOM V - JSX 2
JavaScript
medium
3 likes
132. the angle between hour hand and minute hand of a clock
JavaScript
medium
3 likes
126. BigDecimal addition
JavaScript
Algorithm
medium
3 likes
114. implement BigInt multiplication
JavaScript
medium
3 likes
76. implement BigInt addition with sign
JavaScript
medium
3 likes
77. implement BigInt subtraction with sign
JavaScript
medium
2 likes
129. BigDecimal Division
JavaScript
Algorithm
medium
1 likes
128. BigDecimal multiplication
JavaScript
Algorithm
medium
1 likes
115. implement BigInt division
JavaScript
medium
1 likes
175. CSS Grid Layout auto-placement algorithm - dense
JavaScript
CSS
medium