Front-End coding problems including algorithms and JavaScript ones.

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1. implement curry()JavaScript easy10524 accepted
3. implement Array.prototype.flat()JavaScript easy9181 accepted
4. implement basic throttle()JavaScript Lodash medium7374 accepted
6. implement basic debounce()JavaScript Lodash easy6247 accepted
19. find corresponding node in two identical DOM tree JavaScript easy6074 accepted
16. create an Event Emitter JavaScript medium5539 accepted
17. Create a simple store for DOM element JavaScript easy4367 accepted
28. implement clearAllTimeout()JavaScript easy3902 accepted
14. Implement a general memoization function - `memo()`JavaScript medium3892 accepted
2. implement curry() with placeholder support JavaScript medium3568 accepted
11. what is Composition? create a pipe()JavaScript easy3511 accepted
18. Improve a function JavaScript easy3489 accepted
58. get DOM tree height JavaScript Algorithm DOM medium3417 accepted
32. implement `Promise.all()`JavaScript medium3022 accepted
9. decode message JavaScript medium2759 accepted
10. first bad version JavaScript Algorithm medium2740 accepted
7. implement debounce() with leading & trailing option JavaScript Lodash medium2675 accepted
8. can you shuffle() an array?JavaScript easy2605 accepted
23. create a sum()JavaScript easy2544 accepted
5. implement throttle() with leading & trailing option JavaScript Lodash medium2544 accepted
151. implement Array.prototype.map()JavaScript medium2533 accepted
113. Virtual DOM I JavaScript Algorithm DOM medium2370 accepted
15. implement a simple DOM wrapper to support method chaining like jQuery JavaScript easy2338 accepted
162. find the single integer JavaScript Algorithm easy2204 accepted
25. Reorder array with new indexes JavaScript Algorithm easy2116 accepted
161. toBe() or not.toBe()JavaScript medium2017 accepted
155. create a count function JavaScript easy1999 accepted
159. implement promisify()JavaScript easy1932 accepted
154. Two-way binding JavaScript DOM easy1882 accepted
165. remove characters Algorithm easy1881 accepted
148. create a counter object JavaScript easy1862 accepted
68. get DOM tags JavaScript Algorithm DOM easy1862 accepted
29. implement async helper - `sequence()`JavaScript medium1832 accepted
104. Traverse DOM level by level JavaScript Algorithm DOM easy1830 accepted
33. implement `Promise.allSettled()`JavaScript medium1827 accepted
35. implement `Promise.race()`JavaScript easy1700 accepted
34. implement `Promise.any()`JavaScript medium1693 accepted
57. create an Observable JavaScript medium1662 accepted
89. Next Right Sibling JavaScript DOM Microsoft easy1661 accepted
91. invert a binary tree JavaScript Algorithm easy1621 accepted
110. serialize and deserialize binary tree JavaScript Algorithm medium1557 accepted
92. throttle Promises JavaScript medium1428 accepted
39. implement range()JavaScript easy1391 accepted
13. Implement a Queue by using Stack JavaScript Algorithm ByteDance medium1391 accepted
64. auto-retry Promise on rejection JavaScript medium1380 accepted
167. Intersection of unsorted arrays JavaScript Algorithm easy1351 accepted
146. implement Array.prototype.reduce()JavaScript medium1261 accepted
26. implement Object.assign()JavaScript medium1197 accepted
30. implement async helper - `parallel()`JavaScript medium1186 accepted
157. semver compare JavaScript easy1178 accepted
67. create your own Promise JavaScript Airbnb medium1159 accepted
118. Virtual DOM II - createElement JavaScript easy1157 accepted
158. Previous Left Sibling JavaScript DOM medium1125 accepted
60. create your own `new` operator JavaScript easy1112 accepted
63. create `_.cloneDeep()`JavaScript Algorithm Lodash medium1104 accepted
37. implement Binary Search (unique)JavaScript easy1104 accepted
20. Detect data type in JavaScript JavaScript medium1095 accepted
12. implement Immutability helper JavaScript medium1093 accepted
163. integer to roman numerals JavaScript Algorithm easy1080 accepted
56. call APIs with pagination JavaScript medium1066 accepted
46. implement `_.once()`JavaScript Lodash medium1048 accepted
145. most frequently occurring character JavaScript easy1043 accepted
31. implement async helper - `race()`JavaScript easy1010 accepted
47. reverse a linked list JavaScript Algorithm easy992 accepted
123. implement Promise.prototype.finally()JavaScript medium971 accepted
133. roman numerals to integer JavaScript easy961 accepted
103. implement Math.sqrt()JavaScript Algorithm medium953 accepted
61. create your own `Function.prototype.call`JavaScript medium953 accepted
21. implement JSON.stringify()JavaScript medium934 accepted
122. implement memoizeOne()JavaScript medium927 accepted
125. implement classNames()JavaScript medium914 accepted
140. Virtual DOM III - Functional Component JavaScript easy908 accepted
131. implement _.chunk()JavaScript Lodash medium867 accepted
138. Intersection of two sorted arrays JavaScript Algorithm easy854 accepted
107. Find the largest difference JavaScript Algorithm easy852 accepted
53. write your own `extends` in es5 JavaScript medium847 accepted
94. implement your own `Object.create`JavaScript easy846 accepted
121. A number sequence JavaScript easy839 accepted
130. create LazyMan()JavaScript medium828 accepted
38. implement `jest.spyOn()`JavaScript easy803 accepted
40. implement Bubble Sort JavaScript Algorithm easy776 accepted
69. implement deep equal `_.isEqual()`JavaScript Lodash medium772 accepted
152. Find Top k Elements JavaScript Algorithm medium768 accepted
106. Find two numbers that sum up to 0 JavaScript Algorithm easy754 accepted
85. implement `_.get()`JavaScript Lodash medium752 accepted
120. create `isPrime()`JavaScript Algorithm easy750 accepted
97. compress a string JavaScript string easy749 accepted
66. remove duplicates from an array JavaScript Algorithm medium746 accepted
105. find the first duplicate character in a string JavaScript Apple string easy720 accepted
156. implement `_.set()`JavaScript Lodash medium717 accepted
55. highlight keywords in HTML string JavaScript Algorithm medium703 accepted
54. flatten Thunk JavaScript easy700 accepted
48. search first index with Binary Search(possible duplicate array)JavaScript Algorithm easy694 accepted
168. move zeros JavaScript Algorithm medium693 accepted
81. merge sorted arrays JavaScript Algorithm ByteDance easy679 accepted
36. create a fake timer(setTimeout)JavaScript medium678 accepted
102. validate string of parentheses JavaScript Algorithm string easy677 accepted
86. Generate Fibonacci Number JavaScript Algorithm easy677 accepted
116. implement Object.is()JavaScript easy667 accepted
65. add comma to number JavaScript medium645 accepted
59. create a browser history JavaScript medium640 accepted
24. create a Priority Queue in JavaScript JavaScript Algorithm medium637 accepted
109. implement `Math.pow()`JavaScript Algorithm easy625 accepted
135. localStorage with expiration JavaScript medium611 accepted
49. search last index with Binary Search(possible duplicate array)JavaScript Algorithm easy603 accepted
93. Generate Fibonacci Number with recursion JavaScript easy597 accepted
100. detect circle in linked list JavaScript Algorithm easy594 accepted
139. implement _.partial()JavaScript Lodash medium591 accepted
90. write your own `instanceof`JavaScript medium588 accepted
87. longest substring with unique characters JavaScript Algorithm easy582 accepted
83. create an interval JavaScript ByteDance medium547 accepted
95. implement String.prototype.trim()JavaScript medium544 accepted
79. convert snake_case to camelCase JavaScript medium543 accepted
101. merge identical API calls JavaScript medium541 accepted
117. event delegation JavaScript medium527 accepted
147. Pick up stones JavaScript easy524 accepted
22. implement JSON.parse()JavaScript medium522 accepted
149. interpolation JavaScript medium521 accepted
52. create a middleware system JavaScript medium520 accepted
43. implement Quick Sort JavaScript Algorithm medium510 accepted
27. implement completeAssign() JavaScript medium501 accepted
42. implement Insertion Sort JavaScript Algorithm easy482 accepted
88. support negative Array index in JavaScript JavaScript medium479 accepted
41. implement Merge Sort JavaScript Algorithm medium470 accepted
132. the angle between hour hand and minute hand of a clock JavaScript medium468 accepted
82. find available meeting slots JavaScript Algorithm Airbnb medium468 accepted
50. search element right before target with Binary Search(possible duplicate array)JavaScript Algorithm easy468 accepted
51. search element right after target with Binary Search(possible duplicate array)JavaScript Algorithm easy451 accepted
96. count "1" in binary form JavaScript easy438 accepted
136. find median of two sorted array JavaScript Algorithm medium436 accepted
44. implement Selection Sort JavaScript Algorithm easy424 accepted
153. uglify CSS class names JavaScript medium417 accepted
108. Implement a Stack by using Queue JavaScript Algorithm medium415 accepted
170. Generate CSS Selector for target element JavaScript medium405 accepted
62. implement BigInt addition JavaScript Algorithm easy404 accepted
45. find the K-th largest element in an unsorted array JavaScript Algorithm medium404 accepted
119. create a tokenizer JavaScript medium402 accepted
111. Count palindromic substrings JavaScript Algorithm string easy377 accepted
112. remove duplicate characters in a string JavaScript Algorithm string medium360 accepted
80. implement your own URLSearchParams JavaScript hard?357 accepted
70. implement Observable.from()JavaScript medium340 accepted
99. extract all anchor element from HTML string JavaScript medium334 accepted
142. lit-html 1 - tagged templates JavaScript lit-html easy327 accepted
166. validate number string JavaScript Algorithm string medium324 accepted
134. create your own Cookie JavaScript medium308 accepted
84. create a fake timer (setInterval)JavaScript medium306 accepted
137. binary tree vertical traversal JavaScript Algorithm hard?283 accepted
71. implement Observable Subject JavaScript medium279 accepted
172. implement `Math.clz32()`JavaScript medium274 accepted
72. implement Observable interval()JavaScript easy257 accepted
164. implement Immer produce()JavaScript medium250 accepted
73. implement Observable fromEvent()JavaScript easy239 accepted
74. implement Observable Transformation Operators JavaScript easy236 accepted
98. validate an IP address JavaScript medium230 accepted
75. implement BigInt subtraction JavaScript Algorithm medium220 accepted
78. convert HEX color to RGBA JavaScript medium183 accepted
143. Virtual DOM IV - JSX 1 JavaScript medium168 accepted
169. LRU - Chrome storage automatic eviction JavaScript Algorithm medium132 accepted
124. calculate arithmetic expression JavaScript Algorithm medium132 accepted
171. create callback on message channel JavaScript medium130 accepted
141. implement btoa()JavaScript easy128 accepted
160. implement atob()JavaScript medium105 accepted
150. Virtual DOM V - JSX 2 JavaScript medium91 accepted
76. implement BigInt addition with sign JavaScript medium91 accepted
144. serialize and deserialize data types not supported in JSON JavaScript medium80 accepted
173. uncompress string JavaScript string algorithm medium62 accepted
114. implement BigInt multiplication JavaScript medium54 accepted
77. implement BigInt subtraction with sign JavaScript easy45 accepted
126. BigDecimal addition JavaScript Algorithm medium34 accepted
115. implement BigInt division JavaScript medium27 accepted
128. BigDecimal multiplication JavaScript Algorithm medium15 accepted
129. BigDecimal Division JavaScript Algorithm few challengers10 accepted
127. BigDecimal subtraction JavaScript Algorithm few challengers9 accepted
174. CSS Grid Layout auto-placement algorithm - sparse JavaScript CSS few challengers3 accepted
175. CSS Grid Layout auto-placement algorithm - dense JavaScript CSS few challengers2 accepted