Front-End coding problems including algorithms and JavaScript ones.

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1. implement curry()JavaScript easy5949 accepted
3. implement Array.prototype.flat()JavaScript medium5302 accepted
4. implement basic throttle()JavaScript Lodash medium4166 accepted
6. implement basic debounce()JavaScript Lodash easy3525 accepted
19. find corresponding node in two identical DOM tree JavaScript easy3340 accepted
16. create an Event Emitter JavaScript medium3057 accepted
17. Create a simple store for DOM element JavaScript easy2353 accepted
11. what is Composition? create a pipe()JavaScript easy2099 accepted
58. get DOM tree height JavaScript Algorithm DOM medium1948 accepted
32. implement `Promise.all()`JavaScript medium1919 accepted
14. Implement a general memoization function - `memo()`JavaScript medium1919 accepted
28. implement clearAllTimeout()JavaScript easy1911 accepted
18. Improve a function JavaScript easy1910 accepted
2. implement curry() with placeholder support JavaScript medium1910 accepted
9. decode message JavaScript medium1782 accepted
151. implement Array.prototype.map()JavaScript medium1663 accepted
10. first bad version JavaScript Algorithm medium1660 accepted
8. can you shuffle() an array?JavaScript medium1588 accepted
162. find the single integer JavaScript Algorithm easy1560 accepted
23. create a sum()JavaScript easy1550 accepted
7. implement debounce() with leading & trailing option JavaScript Lodash medium1505 accepted
5. implement throttle() with leading & trailing option JavaScript Lodash medium1428 accepted
155. create a count function JavaScript easy1362 accepted
15. implement a simple DOM wrapper to support method chaining like jQuery JavaScript easy1310 accepted
25. Reorder array with new indexes JavaScript Algorithm easy1296 accepted
148. create a counter object JavaScript easy1273 accepted
159. implement promisify()JavaScript easy1195 accepted
29. implement async helper - `sequence()`JavaScript medium1190 accepted
113. Virtual DOM I JavaScript Algorithm DOM medium1143 accepted
104. Traverse DOM level by level JavaScript Algorithm DOM medium1097 accepted
33. implement `Promise.allSettled()`JavaScript medium1071 accepted
35. implement `Promise.race()`JavaScript easy1024 accepted
68. get DOM tags JavaScript Algorithm DOM medium1007 accepted
161. toBe() or not.toBe()JavaScript medium1002 accepted
34. implement `Promise.any()`JavaScript medium994 accepted
154. Two-way binding JavaScript DOM easy981 accepted
57. create an Observable JavaScript medium957 accepted
39. implement range()JavaScript easy945 accepted
64. auto-retry Promise on rejection JavaScript medium924 accepted
92. throttle Promises JavaScript medium923 accepted
165. remove characters Algorithm easy905 accepted
91. invert a binary tree JavaScript Algorithm easy887 accepted
89. Next Right Sibling JavaScript DOM Microsoft easy884 accepted
13. Implement a Queue by using Stack JavaScript Algorithm ByteDance medium878 accepted
26. implement Object.assign()JavaScript medium818 accepted
146. implement Array.prototype.reduce()JavaScript medium817 accepted
110. serialize and deserialize binary tree JavaScript Algorithm medium810 accepted
157. semver compare JavaScript easy804 accepted
30. implement async helper - `parallel()`JavaScript medium790 accepted
63. create `_.cloneDeep()`JavaScript Algorithm Lodash medium749 accepted
145. most frequently occurring character JavaScript easy745 accepted
12. implement Immutability helper JavaScript medium727 accepted
20. Detect data type in JavaScript JavaScript medium725 accepted
158. Previous Left Sibling JavaScript DOM medium715 accepted
60. create your own `new` operator JavaScript easy708 accepted
47. reverse a linked list JavaScript Algorithm easy700 accepted
56. call APIs with pagination JavaScript medium696 accepted
37. implement Binary Search (unique)JavaScript easy686 accepted
67. create your own Promise JavaScript Airbnb medium676 accepted
163. integer to roman numerals JavaScript Algorithm easy675 accepted
46. implement `_.once()`JavaScript Lodash medium661 accepted
131. implement _.chunk()JavaScript Lodash medium660 accepted
31. implement async helper - `race()`JavaScript easy655 accepted
123. implement Promise.prototype.finally()JavaScript medium651 accepted
138. Intersection of two sorted arrays JavaScript Algorithm easy636 accepted
122. implement memoizeOne()JavaScript medium612 accepted
61. create your own `Function.prototype.call`JavaScript medium596 accepted
107. Find the largest difference JavaScript Algorithm easy589 accepted
53. write your own `extends` in es5 JavaScript medium585 accepted
103. implement Math.sqrt()JavaScript Algorithm medium584 accepted
133. roman numerals to integer JavaScript easy581 accepted
121. A number sequence JavaScript easy553 accepted
118. Virtual DOM II - createElement JavaScript easy550 accepted
152. Find Top k Elements JavaScript Algorithm medium540 accepted
130. create LazyMan()JavaScript medium536 accepted
120. create `isPrime()`JavaScript Algorithm easy533 accepted
106. Find two numbers that sum up to 0 JavaScript Algorithm easy532 accepted
21. implement JSON.stringify()JavaScript medium527 accepted
66. remove duplicates from an array JavaScript Algorithm medium520 accepted
94. implement your own `Object.create`JavaScript easy511 accepted
85. implement `_.get()`JavaScript Lodash medium499 accepted
105. find the first duplicate character in a string JavaScript Apple easy496 accepted
38. implement `jest.spyOn()`JavaScript easy496 accepted
40. implement Bubble Sort JavaScript Algorithm easy490 accepted
69. implement deep equal `_.isEqual()`JavaScript Lodash medium477 accepted
156. implement `_.set()`JavaScript Lodash medium473 accepted
55. highlight keywords in HTML string JavaScript Algorithm medium472 accepted
97. compress a string JavaScript medium471 accepted
54. flatten Thunk JavaScript easy469 accepted
102. validate string of parentheses JavaScript Algorithm easy462 accepted
135. localStorage with expiration JavaScript medium460 accepted
59. create a browser history JavaScript medium451 accepted
24. create a Priority Queue in JavaScript JavaScript Algorithm medium439 accepted
109. implement `Math.pow()`JavaScript Algorithm easy438 accepted
65. add comma to number JavaScript medium438 accepted
48. search first index with Binary Search(possible duplicate array)JavaScript Algorithm easy437 accepted
139. implement _.partial()JavaScript Lodash medium436 accepted
86. Generate Fibonacci Number JavaScript Algorithm medium434 accepted
81. merge sorted arrays JavaScript Algorithm ByteDance easy429 accepted
93. Generate Fibonacci Number with recursion JavaScript easy418 accepted
140. Virtual DOM III - Functional Component JavaScript medium415 accepted
36. create a fake timer(setTimeout)JavaScript medium407 accepted
125. implement classNames()JavaScript medium393 accepted
116. implement Object.is()JavaScript easy391 accepted
49. search last index with Binary Search(possible duplicate array)JavaScript Algorithm easy390 accepted
83. create an interval JavaScript ByteDance medium387 accepted
87. longest substring with unique characters JavaScript Algorithm easy386 accepted
95. implement String.prototype.trim()JavaScript medium385 accepted
100. detect circle in linked list JavaScript Algorithm easy383 accepted
90. write your own `instanceof`JavaScript medium375 accepted
117. event delegation JavaScript medium363 accepted
52. create a middleware system JavaScript medium358 accepted
79. convert snake_case to camelCase JavaScript medium357 accepted
88. support negative Array index in JavaScript JavaScript medium338 accepted
147. Pick up stones JavaScript easy337 accepted
22. implement JSON.parse()JavaScript medium321 accepted
101. merge identical API calls JavaScript medium320 accepted
82. find available meeting slots JavaScript Algorithm Airbnb medium317 accepted
27. implement completeAssign() JavaScript medium317 accepted
51. search element right after target with Binary Search(possible duplicate array)JavaScript Algorithm easy316 accepted
149. interpolation JavaScript medium315 accepted
136. find median of two sorted array JavaScript Algorithm medium313 accepted
50. search element right before target with Binary Search(possible duplicate array)JavaScript Algorithm easy306 accepted
43. implement Quick Sort JavaScript Algorithm medium303 accepted
42. implement Insertion Sort JavaScript Algorithm easy303 accepted
41. implement Merge Sort JavaScript Algorithm medium302 accepted
153. uglify CSS class names JavaScript medium295 accepted
108. Implement a Stack by using Queue JavaScript Algorithm medium290 accepted
96. count "1" in binary form JavaScript easy287 accepted
119. create a tokenizer JavaScript medium284 accepted
132. the angle between hour hand and minute hand of a clock JavaScript U-NEXT medium278 accepted
44. implement Selection Sort JavaScript Algorithm easy275 accepted
62. implement BigInt addition JavaScript Algorithm easy269 accepted
111. Count palindromic substrings JavaScript Algorithm medium259 accepted
80. implement your own URLSearchParams JavaScript medium254 accepted
45. find the K-th largest element in an unsorted array JavaScript Algorithm medium248 accepted
112. remove duplicate characters in a string JavaScript Algorithm medium238 accepted
99. extract all anchor element from HTML string JavaScript medium238 accepted
70. implement Observable.from()JavaScript medium231 accepted
142. lit-html 1 - tagged templates JavaScript lit-html easy218 accepted
84. create a fake timer (setInterval)JavaScript medium205 accepted
137. binary tree vertical traversal JavaScript Algorithm hard?203 accepted
134. create your own Cookie JavaScript hard?192 accepted
72. implement Observable interval()JavaScript easy189 accepted
71. implement Observable Subject JavaScript medium189 accepted
98. validate an IP address JavaScript medium171 accepted
74. implement Observable Transformation Operators JavaScript easy166 accepted
73. implement Observable fromEvent()JavaScript easy161 accepted
75. implement BigInt subtraction JavaScript Algorithm medium129 accepted
78. convert HEX color to RGBA JavaScript medium125 accepted
164. implement Immer produce()JavaScript medium118 accepted
143. Virtual DOM IV - JSX 1 JavaScript medium112 accepted
124. calculate arithmetic expression JavaScript Algorithm medium105 accepted
141. implement btoa()JavaScript easy74 accepted
144. serialize and deserialize data types not supported in JSON JavaScript medium69 accepted
160. implement atob()JavaScript medium65 accepted
76. implement BigInt addition with sign JavaScript medium54 accepted
114. implement BigInt multiplication JavaScript medium43 accepted
77. implement BigInt subtraction with sign JavaScript few challengers31 accepted
150. Virtual DOM V - JSX 2 JavaScript hard?28 accepted
167. Intersection of unsorted arrays JavaScript Algorithm21 accepted
126. BigDecimal addition JavaScript Algorithm medium18 accepted
166. validate number string JavaScript Algorithm17 accepted
115. implement BigInt division JavaScript medium16 accepted
128. BigDecimal multiplication JavaScript Algorithm few challengers13 accepted
129. BigDecimal Division JavaScript Algorithm few challengers8 accepted
127. BigDecimal subtraction JavaScript Algorithm few challengers6 accepted