JavaScript Coding Questions

As a Front-End developer, JavaScript is the core skill of everything

• 1. implement curry()JavaScripteasy30923 accepted
• 3. implement Array.prototype.flat()JavaScriptmedium23566 accepted
• 4. implement basic throttle()JavaScriptLodashmedium17214 accepted
• 6. implement basic debounce()JavaScriptLodasheasy16687 accepted
• 19. find corresponding node in two identical DOM treeJavaScripteasy10498 accepted
• 16. create an Event EmitterJavaScriptmedium10403 accepted
• 11. what is Composition? create a pipe()JavaScripteasy9424 accepted
• 2. implement curry() with placeholder supportJavaScriptmedium8889 accepted
• 17. Create a simple store for DOM elementJavaScripteasy8117 accepted
• 14. Implement a general memoization function - `memo()`JavaScriptmedium8065 accepted
• 32. implement `Promise.all()`JavaScriptmedium8025 accepted
• 18. Improve a functionJavaScripteasy7299 accepted
• 8. can you shuffle() an array?JavaScripteasy7118 accepted
• 28. implement clearAllTimeout()JavaScripteasy7001 accepted
• 176. undefined to nullJavaScripteasy6554 accepted
• 23. create a sum()JavaScriptmedium6337 accepted
• 7. implement debounce() with leading & trailing optionJavaScriptLodashmedium6208 accepted
• 9. decode messageJavaScriptmedium6079 accepted
• 5. implement throttle() with leading & trailing optionJavaScriptLodashmedium5929 accepted
• 10. first bad versionJavaScriptAlgorithmmedium5912 accepted
• 167. Intersection of unsorted arraysJavaScriptAlgorithmeasy5590 accepted
• 58. get DOM tree heightJavaScriptAlgorithmDOMmedium5351 accepted
• 151. implement Array.prototype.map()JavaScriptmedium5199 accepted
• 15. implement a simple DOM wrapper to support method chaining like jQueryJavaScripteasy5046 accepted
• 25. Reorder array with new indexesJavaScriptAlgorithmeasy5041 accepted
• 162. find the single integerJavaScriptAlgorithmeasy4757 accepted
• 35. implement `Promise.race()`JavaScripteasy4432 accepted
• 29. implement async helper - `sequence()`JavaScriptmedium4376 accepted
• 33. implement `Promise.allSettled()`JavaScriptmedium4354 accepted
• 165. remove charactersAlgorithmmedium4346 accepted
• 155. create a count functionJavaScripteasy4279 accepted
• 34. implement `Promise.any()`JavaScriptmedium4202 accepted
• 159. implement promisify()JavaScripteasy4142 accepted
• 64. auto-retry Promise on rejectionJavaScriptmedium4093 accepted
• 92. throttle PromisesJavaScriptmedium3857 accepted
• 148. create a counter objectJavaScripteasy3842 accepted
• 113. Virtual DOM IJavaScriptAlgorithmDOMmedium3748 accepted
• 161. toBe() or not.toBe()JavaScriptmedium3433 accepted
• 13. Implement a Queue by using StackJavaScriptAlgorithmmedium3396 accepted
• 154. Two-way bindingJavaScriptDOMeasy3205 accepted
• 39. implement range()JavaScripteasy3107 accepted
• 57. create an ObservableJavaScriptmedium2990 accepted
• 104. Traverse DOM level by levelJavaScriptAlgorithmDOMmedium2986 accepted
• 146. implement Array.prototype.reduce()JavaScriptmedium2986 accepted
• 68. get DOM tagsJavaScriptAlgorithmDOMmedium2921 accepted
• 91. invert a binary treeJavaScriptAlgorithmeasy2894 accepted
• 30. implement async helper - `parallel()`JavaScriptmedium2816 accepted
• 67. create your own PromiseJavaScriptmedium2797 accepted
• 20. Detect data type in JavaScriptJavaScriptmedium2756 accepted
• 26. implement Object.assign()JavaScriptmedium2726 accepted
• 12. implement Immutability helperJavaScriptmedium2689 accepted
• 89. Next Right SiblingJavaScriptDOMeasy2630 accepted
• 37. implement Binary Search (unique)JavaScripteasy2620 accepted
• 157. semver compareJavaScripteasy2610 accepted
• 168. move zerosJavaScriptAlgorithmmedium2540 accepted
• 31. implement async helper - `race()`JavaScripteasy2499 accepted
• 46. implement `_.once()`JavaScriptLodashmedium2495 accepted
• 60. create your own `new` operatorJavaScripteasy2460 accepted
• 63. create `_.cloneDeep()`JavaScriptAlgorithmLodashmedium2459 accepted
• 110. serialize and deserialize binary treeJavaScriptAlgorithmmedium2424 accepted
• 47. reverse a linked listJavaScriptAlgorithmeasy2361 accepted
• 40. implement Bubble SortJavaScriptAlgorithmeasy2241 accepted
• 21. implement JSON.stringify()JavaScripthard?2212 accepted
• 145. most frequently occurring characterJavaScripteasy2197 accepted
• 56. call APIs with paginationJavaScriptmedium2181 accepted
• 85. implement `_.get()`JavaScriptLodashmedium2105 accepted
• 61. create your own `Function.prototype.call`JavaScriptmedium2082 accepted
• 118. Virtual DOM II - createElementJavaScripteasy2032 accepted
• 133. roman numerals to integerJavaScripteasy2024 accepted
• 125. implement classNames()JavaScriptmedium1994 accepted
• 69. implement deep equal `_.isEqual()`JavaScriptLodashmedium1969 accepted
• 123. implement Promise.prototype.finally()JavaScriptmedium1967 accepted
• 103. implement Math.sqrt()JavaScriptAlgorithmmedium1954 accepted
• 163. integer to roman numeralsJavaScriptAlgorithmeasy1942 accepted
• 81. merge sorted arraysJavaScriptAlgorithmeasy1858 accepted
• 121. A number sequence JavaScripteasy1801 accepted
• 107. Find the largest differenceJavaScriptAlgorithmeasy1800 accepted
• 105. find the first duplicate character in a stringJavaScriptstringeasy1783 accepted
• 83. create an intervalJavaScriptmedium1779 accepted
• 38. implement `jest.spyOn()`JavaScripteasy1763 accepted
• 130. create LazyMan()JavaScriptmedium1687 accepted
• 173. uncompress stringJavaScriptstringalgorithmmedium1663 accepted
• 48. search first index with Binary Search(possible duplicate array)JavaScriptAlgorithmeasy1656 accepted
• 102. validate string of parenthesesJavaScriptAlgorithmstringeasy1652 accepted
• 120. create `isPrime()`JavaScriptAlgorithmeasy1627 accepted
• 106. Find two numbers that sum up to 0JavaScriptAlgorithmeasy1624 accepted
• 94. implement your own `Object.create`JavaScripteasy1623 accepted
• 158. Previous Left SiblingJavaScriptDOMmedium1616 accepted
• 138. Intersection of two sorted arraysJavaScriptAlgorithmeasy1611 accepted
• 53. write your own `extends` in es5JavaScriptmedium1603 accepted
• 87. longest substring with unique charactersJavaScriptAlgorithmeasy1595 accepted
• 122. implement memoizeOne()JavaScriptmedium1540 accepted
• 131. implement _.chunk()JavaScriptLodashmedium1528 accepted
• 54. flatten ThunkJavaScripteasy1524 accepted
• 140. Virtual DOM III - Functional ComponentJavaScripteasy1514 accepted
• 86. Generate Fibonacci NumberJavaScriptAlgorithmmedium1505 accepted
• 97. compress a stringJavaScriptstringeasy1472 accepted
• 66. remove duplicates from an arrayJavaScriptAlgorithmmedium1414 accepted
• 49. search last index with Binary Search(possible duplicate array)JavaScriptAlgorithmeasy1353 accepted
• 109. implement `Math.pow()`JavaScriptAlgorithmeasy1353 accepted
• 116. implement Object.is()JavaScripteasy1349 accepted
• 36. create a fake timer(setTimeout)JavaScriptmedium1314 accepted
• 42. implement Insertion SortJavaScriptAlgorithmeasy1309 accepted
• 156. implement `_.set()`JavaScriptLodashmedium1306 accepted
• 24. create a Priority Queue in JavaScriptJavaScriptAlgorithmmedium1295 accepted
• 135. localStorage with expirationJavaScriptmedium1281 accepted
• 65. add comma to numberJavaScriptmedium1273 accepted
• 59. create a browser historyJavaScriptmedium1261 accepted
• 90. write your own `instanceof`JavaScriptmedium1230 accepted
• 152. Find Top k ElementsJavaScriptAlgorithmmedium1230 accepted
• 147. Pick up stonesJavaScripteasy1206 accepted
• 93. Generate Fibonacci Number with recursionJavaScripteasy1204 accepted
• 55. highlight keywords in HTML stringJavaScriptAlgorithmmedium1184 accepted
• 22. implement JSON.parse()JavaScriptmedium1175 accepted
• 100. detect circle in linked listJavaScriptAlgorithmeasy1175 accepted
• 43. implement Quick SortJavaScriptAlgorithmmedium1155 accepted
• 27. implement completeAssign() JavaScriptmedium1141 accepted
• 44. implement Selection SortJavaScriptAlgorithmeasy1123 accepted
• 41. implement Merge SortJavaScriptAlgorithmmedium1110 accepted
• 50. search element right before target with Binary Search(possible duplicate array)JavaScriptAlgorithmeasy1108 accepted
• 101. merge identical API callsJavaScriptmedium1090 accepted
• 139. implement _.partial()JavaScriptLodashmedium1067 accepted
• 52. create a middleware systemJavaScriptmedium1053 accepted
• 95. implement String.prototype.trim()JavaScriptmedium988 accepted
• 82. find available meeting slotsJavaScriptAlgorithmmedium986 accepted
• 79. convert snake_case to camelCaseJavaScriptmedium978 accepted
• 51. search element right after target with Binary Search(possible duplicate array)JavaScriptAlgorithmeasy956 accepted
• 170. Generate CSS Selector for target elementJavaScriptmedium945 accepted
• 96. count "1" in binary formJavaScripteasy896 accepted
• 88. support negative Array index in JavaScriptJavaScriptmedium879 accepted
• 45. find the K-th largest element in an unsorted arrayJavaScriptAlgorithmmedium876 accepted
• 62. implement BigInt additionJavaScriptAlgorithmeasy860 accepted
• 166. validate number stringJavaScriptAlgorithmstringmedium856 accepted
• 117. event delegationJavaScriptmedium822 accepted
• 136. find median of two sorted arrayJavaScriptAlgorithmmedium813 accepted
• 149. interpolationJavaScriptmedium799 accepted
• 111. Count palindromic substringsJavaScriptAlgorithmstringmedium735 accepted
• 108. Implement a Stack by using QueueJavaScriptAlgorithmmedium715 accepted
• 132. the angle between hour hand and minute hand of a clockJavaScriptmedium697 accepted
• 142. lit-html 1 - tagged templatesJavaScriptlit-htmleasy693 accepted
• 177. Implement Object.groupBy()JavaScriptmedium687 accepted
• 119. create a tokenizerJavaScriptmedium664 accepted
• 112. remove duplicate characters in a stringJavaScriptAlgorithmstringmedium626 accepted
• 134. create your own CookieJavaScriptmedium621 accepted
• 153. uglify CSS class namesJavaScriptmedium599 accepted
• 172. implement `Math.clz32()`JavaScriptmedium593 accepted
• 70. implement Observable.from()JavaScriptmedium584 accepted
• 80. implement your own URLSearchParamsJavaScripthard?576 accepted
• 84. create a fake timer (setInterval)JavaScriptmedium551 accepted
• 137. binary tree vertical traversalJavaScriptAlgorithmhard?546 accepted
• 71. implement Observable SubjectJavaScriptmedium524 accepted
• 171. create callback on message channelJavaScriptmedium495 accepted
• 99. extract all anchor element from HTML string JavaScriptmedium493 accepted
• 72. implement Observable interval()JavaScripteasy486 accepted
• 164. implement Immer produce()JavaScriptmedium475 accepted
• 75. implement BigInt subtractionJavaScriptAlgorithmmedium467 accepted
• 74. implement Observable Transformation OperatorsJavaScripteasy438 accepted
• 73. implement Observable fromEvent()JavaScripteasy419 accepted
• 98. validate an IP addressJavaScriptmedium405 accepted
• 169. LRU - Chrome storage automatic evictionJavaScriptAlgorithmmedium382 accepted
• 78. convert HEX color to RGBAJavaScriptmedium342 accepted
• 143. Virtual DOM IV - JSX 1JavaScriptmedium312 accepted
• 141. implement btoa()JavaScripteasy277 accepted
• 124. calculate arithmetic expressionJavaScriptAlgorithmmedium246 accepted
• 76. implement BigInt addition with signJavaScriptmedium221 accepted
• 160. implement atob()JavaScriptmedium199 accepted
• 144. serialize and deserialize data types not supported in JSONJavaScriptmedium173 accepted
• 114. implement BigInt multiplicationJavaScriptmedium170 accepted
• 150. Virtual DOM V - JSX 2JavaScriptmedium167 accepted
• 77. implement BigInt subtraction with signJavaScriptmedium133 accepted
• 115. implement BigInt divisionJavaScriptmedium83 accepted
• 126. BigDecimal additionJavaScriptAlgorithmmedium82 accepted
• 174. CSS Grid Layout auto-placement algorithm - sparseJavaScriptCSShard?58 accepted
• 128. BigDecimal multiplicationJavaScriptAlgorithmmedium46 accepted
• 129. BigDecimal DivisionJavaScriptAlgorithmmedium44 accepted
• 127. BigDecimal subtractionJavaScriptAlgorithmmedium39 accepted
• 175. CSS Grid Layout auto-placement algorithm - denseJavaScriptCSSmedium21 accepted