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JavaScript Coding Questions
As a Front-End developer, JavaScript is the core skill of everything
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Difficulty
Solved status
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Sort: most accepted
Difficulty: medium
4. implement basic throttle()
JavaScript
Lodash
medium
12812 accepted
16. create an Event Emitter
JavaScript
medium
8214 accepted
2. implement curry() with placeholder support
JavaScript
medium
6437 accepted
14. Implement a general memoization function - `memo()`
JavaScript
medium
6134 accepted
32. implement `Promise.all()`
JavaScript
medium
5844 accepted
8. can you shuffle() an array?
JavaScript
medium
5049 accepted
9. decode message
JavaScript
medium
4599 accepted
58. get DOM tree height
JavaScript
Algorithm
DOM
medium
4564 accepted
10. first bad version
JavaScript
Algorithm
medium
4564 accepted
7. implement debounce() with leading & trailing option
JavaScript
Lodash
medium
4561 accepted
5. implement throttle() with leading & trailing option
JavaScript
Lodash
medium
4402 accepted
151. implement Array.prototype.map()
JavaScript
medium
4162 accepted
165. remove characters
Algorithm
medium
3739 accepted
33. implement `Promise.allSettled()`
JavaScript
medium
3173 accepted
29. implement async helper - `sequence()`
JavaScript
medium
3135 accepted
113. Virtual DOM I
JavaScript
Algorithm
DOM
medium
3091 accepted
34. implement `Promise.any()`
JavaScript
medium
3056 accepted
161. toBe() or not.toBe()
JavaScript
medium
2784 accepted
92. throttle Promises
JavaScript
medium
2689 accepted
64. auto-retry Promise on rejection
JavaScript
medium
2624 accepted
13. Implement a Queue by using Stack
JavaScript
Algorithm
medium
2553 accepted
68. get DOM tags
JavaScript
Algorithm
DOM
medium
2524 accepted
104. Traverse DOM level by level
JavaScript
Algorithm
DOM
medium
2522 accepted
57. create an Observable
JavaScript
medium
2467 accepted
146. implement Array.prototype.reduce()
JavaScript
medium
2335 accepted
67. create your own Promise
JavaScript
medium
2112 accepted
26. implement Object.assign()
JavaScript
medium
2105 accepted
110. serialize and deserialize binary tree
JavaScript
Algorithm
medium
2071 accepted
30. implement async helper - `parallel()`
JavaScript
medium
2013 accepted
12. implement Immutability helper
JavaScript
medium
2011 accepted
168. move zeros
JavaScript
Algorithm
medium
1993 accepted
20. Detect data type in JavaScript
JavaScript
medium
1989 accepted
63. create `_.cloneDeep()`
JavaScript
Algorithm
Lodash
medium
1805 accepted
21. implement JSON.stringify()
JavaScript
medium
1764 accepted
56. call APIs with pagination
JavaScript
medium
1699 accepted
123. implement Promise.prototype.finally()
JavaScript
medium
1587 accepted
61. create your own `Function.prototype.call`
JavaScript
medium
1573 accepted
103. implement Math.sqrt()
JavaScript
Algorithm
medium
1540 accepted
158. Previous Left Sibling
JavaScript
DOM
medium
1488 accepted
85. implement `_.get()`
JavaScript
Lodash
medium
1459 accepted
125. implement classNames()
JavaScript
medium
1442 accepted
53. write your own `extends` in es5
JavaScript
medium
1345 accepted
69. implement deep equal `_.isEqual()`
JavaScript
Lodash
medium
1336 accepted
131. implement _.chunk()
JavaScript
Lodash
medium
1284 accepted
130. create LazyMan()
JavaScript
medium
1278 accepted
122. implement memoizeOne()
JavaScript
medium
1268 accepted
86. Generate Fibonacci Number
JavaScript
Algorithm
medium
1187 accepted
83. create an interval
JavaScript
medium
1159 accepted
66. remove duplicates from an array
JavaScript
Algorithm
medium
1147 accepted
173. uncompress string
JavaScript
string
algorithm
medium
1129 accepted
152. Find Top k Elements
JavaScript
Algorithm
medium
1081 accepted
36. create a fake timer(setTimeout)
JavaScript
medium
1079 accepted
156. implement `_.set()`
JavaScript
Lodash
medium
1077 accepted
90. write your own `instanceof`
JavaScript
medium
1021 accepted
24. create a Priority Queue in JavaScript
JavaScript
Algorithm
medium
1007 accepted
65. add comma to number
JavaScript
medium
1002 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
962 accepted
27. implement completeAssign()
JavaScript
medium
932 accepted
135. localStorage with expiration
JavaScript
medium
911 accepted
43. implement Quick Sort
JavaScript
Algorithm
medium
895 accepted
101. merge identical API calls
JavaScript
medium
882 accepted
139. implement _.partial()
JavaScript
Lodash
medium
877 accepted
52. create a middleware system
JavaScript
medium
853 accepted
79. convert snake_case to camelCase
JavaScript
medium
829 accepted
95. implement String.prototype.trim()
JavaScript
medium
815 accepted
170. Generate CSS Selector for target element
JavaScript
medium
807 accepted
41. implement Merge Sort
JavaScript
Algorithm
medium
804 accepted
82. find available meeting slots
JavaScript
Algorithm
medium
776 accepted
88. support negative Array index in JavaScript
JavaScript
medium
735 accepted
166. validate number string
JavaScript
Algorithm
string
medium
726 accepted
117. event delegation
JavaScript
medium
716 accepted
149. interpolation
JavaScript
medium
714 accepted
136. find median of two sorted array
JavaScript
Algorithm
medium
692 accepted
45. find the K-th largest element in an unsorted array
JavaScript
Algorithm
medium
668 accepted
111. Count palindromic substrings
JavaScript
Algorithm
string
medium
632 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
551 accepted
153. uglify CSS class names
JavaScript
medium
541 accepted
112. remove duplicate characters in a string
JavaScript
Algorithm
string
medium
530 accepted
172. implement `Math.clz32()`
JavaScript
medium
507 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
398 accepted
164. implement Immer produce()
JavaScript
medium
395 accepted
75. implement BigInt subtraction
JavaScript
Algorithm
medium
369 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
150. Virtual DOM V - JSX 2
JavaScript
medium
129 accepted
114. implement BigInt multiplication
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