Front-End coding problems including algorithms and JavaScript ones.

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1. implement curry()JavaScript medium1850 accepted
3. implement Array.prototype.flat()JavaScript medium1756 accepted
4. implement basic throttle()JavaScript Lodash medium1096 accepted
6. implement basic debounce()JavaScript Lodash easy955 accepted
19. find corresponding node in two identical DOM tree JavaScript medium934 accepted
16. create an Event Emitter JavaScript medium797 accepted
11. what is Composition? create a pipe()JavaScript easy646 accepted
9. decode message JavaScript medium639 accepted
58. get DOM tree height JavaScript Algorithm DOM medium628 accepted
32. implement `Promise.all()`JavaScript medium611 accepted
8. can you shuffle() an array?JavaScript medium611 accepted
17. Create a simple store for DOM element JavaScript easy599 accepted
10. first bad version JavaScript Algorithm medium596 accepted
18. Improve a function JavaScript medium578 accepted
2. implement curry() with placeholder support JavaScript medium575 accepted
14. Implement a general memoization function - `memo()`JavaScript medium550 accepted
23. create a sum()JavaScript medium509 accepted
151. implement Array.prototype.map()JavaScript medium505 accepted
25. Reorder array with new indexes JavaScript Algorithm medium478 accepted
28. implement clearAllTimeout()JavaScript easy453 accepted
104. Traverse DOM level by level JavaScript Algorithm DOM medium420 accepted
148. create a counter object JavaScript easy410 accepted
15. implement a simple DOM wrapper to support method chaining like jQuery JavaScript easy395 accepted
7. implement debounce() with leading & trailing option JavaScript Lodash medium378 accepted
29. implement async helper - `sequence()`JavaScript medium362 accepted
39. implement range()JavaScript easy347 accepted
68. get DOM tags JavaScript Algorithm DOM medium328 accepted
33. implement `Promise.allSettled()`JavaScript medium328 accepted
5. implement throttle() with leading & trailing option JavaScript Lodash medium328 accepted
113. Virtual DOM I JavaScript Algorithm DOM medium327 accepted
64. auto-retry Promise on rejection JavaScript medium321 accepted
13. Implement a Queue by using Stack JavaScript Algorithm ByteDance medium305 accepted
35. implement `Promise.race()`JavaScript easy303 accepted
57. create an Observable JavaScript medium288 accepted
89. Next Right Sibling JavaScript DOM Microsoft medium285 accepted
34. implement `Promise.any()`JavaScript medium285 accepted
26. implement Object.assign()JavaScript medium285 accepted
20. Detect data type in JavaScript JavaScript medium279 accepted
110. serialize and deserialize binary tree JavaScript Algorithm medium266 accepted
92. throttle Promises JavaScript medium266 accepted
131. implement _.chunk()JavaScript Lodash medium257 accepted
91. invert a binary tree JavaScript Algorithm easy257 accepted
46. implement `_.once()`JavaScript Lodash medium251 accepted
37. implement Binary Search (unique)JavaScript easy248 accepted
155. create a count function JavaScript easy241 accepted
30. implement async helper - `parallel()`JavaScript medium239 accepted
63. create `_.cloneDeep()`JavaScript Algorithm Lodash medium234 accepted
146. implement Array.prototype.reduce()JavaScript medium233 accepted
47. reverse a linked list JavaScript Algorithm easy232 accepted
138. Intersection of two sorted arrays JavaScript Algorithm easy227 accepted
60. create your own `new` operator JavaScript medium223 accepted
145. most frequently occurring character JavaScript easy219 accepted
121. A number sequence JavaScript medium219 accepted
107. Find the largest difference JavaScript Algorithm easy218 accepted
31. implement async helper - `race()`JavaScript easy212 accepted
152. Find Top k Elements JavaScript Algorithm medium206 accepted
135. localStorage with expiration JavaScript medium203 accepted
67. create your own Promise JavaScript Airbnb medium203 accepted
12. implement Immutability helper JavaScript medium203 accepted
123. implement Promise.prototype.finally()JavaScript medium200 accepted
53. write your own `extends` in es5 JavaScript medium198 accepted
105. find the first duplicate character in a string JavaScript Apple easy196 accepted
122. implement memoizeOne()JavaScript medium193 accepted
61. create your own `Function.prototype.call`JavaScript medium192 accepted
85. implement `_.get()`JavaScript Lodash medium190 accepted
97. compress a string JavaScript medium189 accepted
56. call APIs with pagination JavaScript medium188 accepted
24. create a Priority Queue in JavaScript JavaScript Algorithm medium182 accepted
106. Find two numbers that sum up to 0 JavaScript Algorithm easy180 accepted
55. highlight keywords in HTML string JavaScript Algorithm medium177 accepted
130. create LazyMan()JavaScript hard?176 accepted
103. implement Math.sqrt()JavaScript Algorithm medium174 accepted
66. remove duplicates from an array JavaScript Algorithm medium173 accepted
118. Virtual DOM II - createElement JavaScript medium170 accepted
139. implement _.partial()JavaScript Lodash medium167 accepted
154. Two-way binding JavaScript DOM easy159 accepted
69. implement deep equal `_.isEqual()`JavaScript Lodash medium156 accepted
65. add comma to number JavaScript medium155 accepted
125. implement classNames()JavaScript medium151 accepted
38. implement `jest.spyOn()`JavaScript medium151 accepted
102. validate string of parentheses JavaScript Algorithm easy148 accepted
59. create a browser history JavaScript medium147 accepted
88. support negative Array index in JavaScript JavaScript medium146 accepted
83. create an interval JavaScript ByteDance medium143 accepted
93. Generate Fibonacci Number with recursion JavaScript easy142 accepted
54. flatten Thunk JavaScript easy142 accepted
120. create `isPrime()`JavaScript Algorithm medium141 accepted
95. implement String.prototype.trim()JavaScript medium140 accepted
79. convert snake_case to camelCase JavaScript medium140 accepted
133. roman numerals to integer JavaScript medium139 accepted
86. Generate Fibonacci Number JavaScript Algorithm medium139 accepted
94. implement your own `Object.create`JavaScript medium137 accepted
40. implement Bubble Sort JavaScript Algorithm easy137 accepted
21. implement JSON.stringify()JavaScript hard?136 accepted
162. find the single integer JavaScript Algorithm easy135 accepted
48. search first index with Binary Search(possible duplicate array)JavaScript Algorithm medium132 accepted
159. implement promisify()JavaScript easy125 accepted
100. detect circle in linked list JavaScript Algorithm easy124 accepted
109. implement `Math.pow()`JavaScript Algorithm easy122 accepted
90. write your own `instanceof`JavaScript medium118 accepted
117. event delegation JavaScript hard?117 accepted
81. merge sorted arrays JavaScript Algorithm ByteDance medium117 accepted
36. create a fake timer(setTimeout)JavaScript medium117 accepted
140. Virtual DOM III - Functional Component JavaScript medium115 accepted
147. Pick up stones JavaScript easy113 accepted
136. find median of two sorted array JavaScript Algorithm medium113 accepted
149. interpolation JavaScript medium112 accepted
116. implement Object.is()JavaScript medium112 accepted
119. create a tokenizer JavaScript medium111 accepted
161. toBe() or not.toBe()JavaScript medium110 accepted
27. implement completeAssign() JavaScript medium107 accepted
157. semver compare JavaScript easy106 accepted
87. longest substring with unique characters JavaScript Algorithm medium105 accepted
52. create a middleware system JavaScript medium105 accepted
96. count "1" in binary form JavaScript easy104 accepted
108. Implement a Stack by using Queue JavaScript Algorithm medium103 accepted
49. search last index with Binary Search(possible duplicate array)JavaScript Algorithm easy102 accepted
99. extract all anchor element from HTML string JavaScript medium97 accepted
82. find available meeting slots JavaScript Algorithm Airbnb medium96 accepted
70. implement Observable.from()JavaScript medium95 accepted
43. implement Quick Sort JavaScript Algorithm medium95 accepted
112. remove duplicate characters in a string JavaScript Algorithm hard?93 accepted
111. Count palindromic substrings JavaScript Algorithm medium90 accepted
132. the angle between hour hand and minute hand of a clock JavaScript U-NEXT medium89 accepted
156. implement `_.set()`JavaScript Lodash medium87 accepted
72. implement Observable interval()JavaScript easy86 accepted
41. implement Merge Sort JavaScript Algorithm medium85 accepted
51. search element right after target with Binary Search(possible duplicate array)JavaScript Algorithm easy84 accepted
42. implement Insertion Sort JavaScript Algorithm easy82 accepted
158. Previous Left Sibling JavaScript DOM medium81 accepted
137. binary tree vertical traversal JavaScript Algorithm hard?81 accepted
80. implement your own URLSearchParams JavaScript hard?80 accepted
153. uglify CSS class names JavaScript medium79 accepted
44. implement Selection Sort JavaScript Algorithm easy79 accepted
22. implement JSON.parse()JavaScript medium79 accepted
50. search element right before target with Binary Search(possible duplicate array)JavaScript Algorithm easy77 accepted
45. find the K-th largest element in an unsorted array JavaScript Algorithm medium77 accepted
62. implement BigInt addition JavaScript Algorithm medium74 accepted
142. lit-html 1 - tagged templates JavaScript lit-html medium72 accepted
101. merge identical API calls JavaScript hard?71 accepted
134. create your own Cookie JavaScript hard?66 accepted
71. implement Observable Subject JavaScript medium62 accepted
73. implement Observable fromEvent()JavaScript easy61 accepted
74. implement Observable Transformation Operators JavaScript easy58 accepted
78. convert HEX color to RGBA JavaScript medium53 accepted
84. create a fake timer (setInterval)JavaScript medium48 accepted
143. Virtual DOM IV - JSX 1 JavaScript medium46 accepted
98. validate an IP address JavaScript medium43 accepted
75. implement BigInt subtraction JavaScript Algorithm medium37 accepted
124. calculate arithmetic expression JavaScript Algorithm medium35 accepted
114. implement BigInt multiplication JavaScript medium20 accepted
76. implement BigInt addition with sign JavaScript medium18 accepted
150. Virtual DOM V - JSX 2 JavaScript hard?11 accepted
141. implement btoa()JavaScript few challengers11 accepted
77. implement BigInt subtraction with sign JavaScript few challengers11 accepted
160. implement atob()JavaScript few challengers9 accepted
126. BigDecimal addition JavaScript Algorithm few challengers8 accepted
115. implement BigInt division JavaScript few challengers8 accepted
144. serialize and deserialize data types not supported in JSON JavaScript few challengers7 accepted
128. BigDecimal multiplication JavaScript Algorithm few challengers7 accepted
129. BigDecimal Division JavaScript Algorithm few challengers4 accepted
127. BigDecimal subtraction JavaScript Algorithm few challengers2 accepted