Front-End coding problems including algorithms and JavaScript ones.

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1. implement curry()JavaScript medium2286 accepted
3. implement Array.prototype.flat()JavaScript medium2145 accepted
4. implement basic throttle()JavaScript Lodash medium1505 accepted
6. implement basic debounce()JavaScript Lodash easy1276 accepted
19. find corresponding node in two identical DOM tree JavaScript medium1214 accepted
16. create an Event Emitter JavaScript medium1099 accepted
32. implement `Promise.all()`JavaScript medium848 accepted
11. what is Composition? create a pipe()JavaScript easy844 accepted
17. Create a simple store for DOM element JavaScript easy804 accepted
58. get DOM tree height JavaScript Algorithm DOM medium799 accepted
9. decode message JavaScript medium780 accepted
8. can you shuffle() an array?JavaScript medium753 accepted
10. first bad version JavaScript Algorithm medium750 accepted
18. Improve a function JavaScript medium749 accepted
14. Implement a general memoization function - `memo()`JavaScript medium743 accepted
151. implement Array.prototype.map()JavaScript medium717 accepted
2. implement curry() with placeholder support JavaScript medium708 accepted
23. create a sum()JavaScript medium645 accepted
28. implement clearAllTimeout()JavaScript easy636 accepted
25. Reorder array with new indexes JavaScript Algorithm medium599 accepted
7. implement debounce() with leading & trailing option JavaScript Lodash medium550 accepted
148. create a counter object JavaScript easy528 accepted
104. Traverse DOM level by level JavaScript Algorithm DOM medium523 accepted
15. implement a simple DOM wrapper to support method chaining like jQuery JavaScript easy519 accepted
29. implement async helper - `sequence()`JavaScript medium506 accepted
162. find the single integer JavaScript Algorithm easy476 accepted
5. implement throttle() with leading & trailing option JavaScript Lodash medium469 accepted
33. implement `Promise.allSettled()`JavaScript medium456 accepted
39. implement range()JavaScript easy442 accepted
64. auto-retry Promise on rejection JavaScript medium430 accepted
113. Virtual DOM I JavaScript Algorithm DOM medium420 accepted
68. get DOM tags JavaScript Algorithm DOM medium410 accepted
35. implement `Promise.race()`JavaScript easy407 accepted
155. create a count function JavaScript easy405 accepted
34. implement `Promise.any()`JavaScript medium403 accepted
26. implement Object.assign()JavaScript medium389 accepted
13. Implement a Queue by using Stack JavaScript Algorithm ByteDance medium381 accepted
92. throttle Promises JavaScript medium373 accepted
20. Detect data type in JavaScript JavaScript medium365 accepted
89. Next Right Sibling JavaScript DOM Microsoft medium364 accepted
57. create an Observable JavaScript medium359 accepted
91. invert a binary tree JavaScript Algorithm easy342 accepted
30. implement async helper - `parallel()`JavaScript medium342 accepted
110. serialize and deserialize binary tree JavaScript Algorithm medium328 accepted
146. implement Array.prototype.reduce()JavaScript medium327 accepted
46. implement `_.once()`JavaScript Lodash medium322 accepted
37. implement Binary Search (unique)JavaScript easy320 accepted
47. reverse a linked list JavaScript Algorithm easy319 accepted
63. create `_.cloneDeep()`JavaScript Algorithm Lodash medium318 accepted
159. implement promisify()JavaScript easy312 accepted
131. implement _.chunk()JavaScript Lodash medium308 accepted
145. most frequently occurring character JavaScript easy307 accepted
138. Intersection of two sorted arrays JavaScript Algorithm easy298 accepted
60. create your own `new` operator JavaScript medium290 accepted
123. implement Promise.prototype.finally()JavaScript medium281 accepted
31. implement async helper - `race()`JavaScript easy281 accepted
107. Find the largest difference JavaScript Algorithm easy279 accepted
161. toBe() or not.toBe()JavaScript medium272 accepted
12. implement Immutability helper JavaScript medium267 accepted
152. Find Top k Elements JavaScript Algorithm medium265 accepted
67. create your own Promise JavaScript Airbnb medium263 accepted
61. create your own `Function.prototype.call`JavaScript medium263 accepted
56. call APIs with pagination JavaScript medium260 accepted
121. A number sequence JavaScript medium252 accepted
154. Two-way binding JavaScript DOM easy249 accepted
53. write your own `extends` in es5 JavaScript medium249 accepted
105. find the first duplicate character in a string JavaScript Apple easy248 accepted
135. localStorage with expiration JavaScript medium241 accepted
24. create a Priority Queue in JavaScript JavaScript Algorithm medium238 accepted
106. Find two numbers that sum up to 0 JavaScript Algorithm easy236 accepted
103. implement Math.sqrt()JavaScript Algorithm medium231 accepted
130. create LazyMan()JavaScript hard?230 accepted
85. implement `_.get()`JavaScript Lodash medium228 accepted
122. implement memoizeOne()JavaScript medium225 accepted
97. compress a string JavaScript medium223 accepted
66. remove duplicates from an array JavaScript Algorithm medium220 accepted
55. highlight keywords in HTML string JavaScript Algorithm medium217 accepted
157. semver compare JavaScript easy216 accepted
69. implement deep equal `_.isEqual()`JavaScript Lodash medium215 accepted
38. implement `jest.spyOn()`JavaScript medium215 accepted
139. implement _.partial()JavaScript Lodash medium209 accepted
158. Previous Left Sibling JavaScript DOM medium203 accepted
118. Virtual DOM II - createElement JavaScript medium203 accepted
65. add comma to number JavaScript medium202 accepted
21. implement JSON.stringify()JavaScript hard?202 accepted
133. roman numerals to integer JavaScript medium195 accepted
120. create `isPrime()`JavaScript Algorithm easy194 accepted
93. Generate Fibonacci Number with recursion JavaScript easy189 accepted
54. flatten Thunk JavaScript easy189 accepted
40. implement Bubble Sort JavaScript Algorithm easy186 accepted
125. implement classNames()JavaScript medium185 accepted
102. validate string of parentheses JavaScript Algorithm easy185 accepted
88. support negative Array index in JavaScript JavaScript medium184 accepted
59. create a browser history JavaScript medium183 accepted
83. create an interval JavaScript ByteDance medium181 accepted
48. search first index with Binary Search(possible duplicate array)JavaScript Algorithm medium180 accepted
95. implement String.prototype.trim()JavaScript medium177 accepted
94. implement your own `Object.create`JavaScript medium176 accepted
86. Generate Fibonacci Number JavaScript Algorithm medium176 accepted
36. create a fake timer(setTimeout)JavaScript medium168 accepted
79. convert snake_case to camelCase JavaScript medium167 accepted
100. detect circle in linked list JavaScript Algorithm easy165 accepted
52. create a middleware system JavaScript medium165 accepted
49. search last index with Binary Search(possible duplicate array)JavaScript Algorithm easy162 accepted
109. implement `Math.pow()`JavaScript Algorithm easy156 accepted
147. Pick up stones JavaScript easy155 accepted
117. event delegation JavaScript medium155 accepted
156. implement `_.set()`JavaScript Lodash medium151 accepted
149. interpolation JavaScript medium150 accepted
116. implement Object.is()JavaScript medium147 accepted
90. write your own `instanceof`JavaScript medium146 accepted
81. merge sorted arrays JavaScript Algorithm ByteDance medium145 accepted
140. Virtual DOM III - Functional Component JavaScript medium144 accepted
136. find median of two sorted array JavaScript Algorithm medium140 accepted
27. implement completeAssign() JavaScript medium139 accepted
96. count "1" in binary form JavaScript easy137 accepted
108. Implement a Stack by using Queue JavaScript Algorithm medium136 accepted
43. implement Quick Sort JavaScript Algorithm medium135 accepted
87. longest substring with unique characters JavaScript Algorithm medium130 accepted
51. search element right after target with Binary Search(possible duplicate array)JavaScript Algorithm easy130 accepted
119. create a tokenizer JavaScript medium129 accepted
42. implement Insertion Sort JavaScript Algorithm easy129 accepted
41. implement Merge Sort JavaScript Algorithm medium122 accepted
22. implement JSON.parse()JavaScript medium121 accepted
82. find available meeting slots JavaScript Algorithm Airbnb medium120 accepted
101. merge identical API calls JavaScript medium116 accepted
80. implement your own URLSearchParams JavaScript hard?115 accepted
99. extract all anchor element from HTML string JavaScript medium114 accepted
50. search element right before target with Binary Search(possible duplicate array)JavaScript Algorithm easy113 accepted
44. implement Selection Sort JavaScript Algorithm easy113 accepted
153. uglify CSS class names JavaScript medium112 accepted
70. implement Observable.from()JavaScript medium111 accepted
111. Count palindromic substrings JavaScript Algorithm medium109 accepted
112. remove duplicate characters in a string JavaScript Algorithm hard?108 accepted
132. the angle between hour hand and minute hand of a clock JavaScript U-NEXT medium106 accepted
45. find the K-th largest element in an unsorted array JavaScript Algorithm medium106 accepted
137. binary tree vertical traversal JavaScript Algorithm hard?105 accepted
62. implement BigInt addition JavaScript Algorithm medium101 accepted
72. implement Observable interval()JavaScript easy99 accepted
163. integer to roman numerals JavaScript Algorithm easy94 accepted
142. lit-html 1 - tagged templates JavaScript lit-html medium86 accepted
134. create your own Cookie JavaScript hard?84 accepted
71. implement Observable Subject JavaScript medium82 accepted
73. implement Observable fromEvent()JavaScript easy74 accepted
74. implement Observable Transformation Operators JavaScript easy72 accepted
84. create a fake timer (setInterval)JavaScript medium64 accepted
78. convert HEX color to RGBA JavaScript medium64 accepted
98. validate an IP address JavaScript medium56 accepted
75. implement BigInt subtraction JavaScript Algorithm medium54 accepted
143. Virtual DOM IV - JSX 1 JavaScript medium46 accepted
124. calculate arithmetic expression JavaScript Algorithm medium42 accepted
76. implement BigInt addition with sign JavaScript medium29 accepted
114. implement BigInt multiplication JavaScript medium24 accepted
160. implement atob()JavaScript few challengers19 accepted
144. serialize and deserialize data types not supported in JSON JavaScript medium17 accepted
77. implement BigInt subtraction with sign JavaScript few challengers16 accepted
141. implement btoa()JavaScript few challengers13 accepted
150. Virtual DOM V - JSX 2 JavaScript hard?11 accepted
115. implement BigInt division JavaScript few challengers9 accepted
126. BigDecimal addition JavaScript Algorithm few challengers8 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