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JavaScript DSA Interview Questions

Coding questions on data structures and algorithms, using JavaScript.
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Questions List

JavaScript Interview GuidesExplore our starter guides to get a solid grasp of JavaScript interview prep before jumping into practice.
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GUIDES
  • Selection SortImplement a function that performs a selection sort
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  • StackImplement a stack data structure containing the common stack methods
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  • Count Set Bits in a Binary NumberImplement a function to find set bits in binary representation of a given integer
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  • Find Duplicates in ArrayImplement a function to check if there are any duplicate numbers in the array
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  • Find Missing Number in SequenceImplement a function to find the missing element in a sorted array
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  • Insertion SortImplement a function that performs an insertion sort
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  • Optimal Stock TradingImplement a function to find the maximum profit achievable by buying and selling a stock once
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  • Pair sumImplement a function to find two numbers within an array of integers that add up to a target integer
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  • String AnagramImplement a function to determine if two strings are anagram of each other
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  • Binary Tree Maximum DepthImplement a function to find the maximum depth of a binary tree
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  • Flip Binary TreeImplement a function to flip the nodes in a binary tree
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  • Staircase Climbing CombinationsImplement a function to find the number of ways to reach at the top of staircase
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  • Balanced BracketsImplement a function to determine if a string contains balanced brackets
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  • Binary Tree EqualImplement a function to determine whether two binary trees are equal
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  • Bit CountingImplement a function to find number of set bits from 0 to n
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  • Bit ReversalImplement a function to flip the order of the bits in a given number
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  • Linked List ReversalImplement a function to reverse a linked list
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  • String PalindromeImplement a function to determine if a string is a palindrome
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  • Linked List Detect CycleImplement a function to detect if there are cycles in a linked list
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  • Binary Tree SubtreeImplement a function to check if a binary tree is a subtree of another binary tree
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  • Linked Lists Combine Two SortedImplement a function to combine two sorted linked list
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  • Meeting CalendarImplement a function to check if all meetings can be attended
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  • Array Product Excluding CurrentImplement a function to find the product of elements in an array excluding the current element
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  • Binary SearchImplement a function that performs binary search on an array of numbers
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  • Breadth-first SearchImplement a breadth-first search algorithm that traverses a directed graph in a breadth-first manner
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  • Depth-first SearchImplement a depth-first search algorithm that traverses a directed graph in a depth-first manner
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  • Heap SortImplement a function that performs a heap sort
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  • Is the Graph a TreeImplement a function to determine if a graph is a valid tree
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  • Maximum Water Trapped Between WallsImplement a function to find the maximum water volume between two walls in an array of walls
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  • QueueImplement a queue data structure containing the common queue methods
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  • Merge SortImplement a function that performs a recursive merge sort
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  • Quick SortImplement a function that performs a recursive quick sort
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  • Topological SortImplement a function that performs a topological sort
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  • Binary Tree Level Order TraversalImplement a function to find the level order traversal of a binary tree
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  • Maximum Sum in Contiguous ArrayImplement a function to find the subarray with the maximum sum
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  • Smallest element in rotated sorted arrayImplement a function to find the smallest element in rotated sorted array
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  • Find Element in Rotated ArrayImplement a function to find an integer in a rotated sorted array
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  • Maximum Product in Contiguous ArrayImplement a function to find the subarray which has the largest product
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  • Binary Search Tree Kth Smallest ElementImplement a function to find the kth smallest node in a BST
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  • Binary Search Tree Lowest Common AncestorImplement a function to find the LCA in a binary search tree
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  • Count Islands in a GridImplement a function to count distinct islands in a 2D binary grid
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  • Delete Nth Node from End of Linked ListImplement a function to delete the nth node from the end of a linked list
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  • Distinct Paths in GridImplement a function to calculate distinct paths for a robot moving on an m x n grid
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  • Matrix ZeroingImplement a function to set matrix rows and columns to zero
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  • Merge Overlapping IntervalsImplement a function to merge overlapping intervals
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  • Most Common ElementsImplement a function to determine the most common elements in an integer array
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  • Neighborhood TheftImplement a function to find maximum money to rob without alerting police
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  • Rearrange Linked ListImplement a function to rearrange the nodes in a linked list
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  • Sum Without AdditionImplement a function to find the sum of two integers without using + and - operator
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  • Triplet SumImplement a function to find all unique triplets with distinct indices that sum to 0
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  • Validate Binary Search TreeImplement a function to validate whether a binary tree is a valid binary search tree
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  • Combinations for Target SumImplement a function to count combinations that sum to the target
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  • Course DependencyImplement a function to check if all courses can be completed given prerequisites
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  • Decode MessageImplement a function to count ways to decode a numeric string
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  • Longest Consecutive Number SequenceImplement a function to find the length of the longest consecutive number sequence
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  • NEW
    Longest Increasing SubsequenceImplement a function to find the length of the longest increasing subsequence
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  • NEW
    Minimum Coins for ChangeImplement a function to return minimum coins needed to make the given amount
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  • Palindromic SubstringsImplement a function to count all palindromic substrings in a string
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  • Segment WordsImplement a function to check whether a string be formed from dictionary words
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  • String Anagram GroupsImplement a function to group an array of strings into anagrams
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  • Task CoordinationImplement a function to find minimum intervals for tasks with cooldown
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  • Trie (Prefix Tree)Implement a trie-prefix-tree with insert, search, and starts with functionality
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  • Binary Tree Rebuilding from Preorder and Inorder TraversalsImplement a function to construct a binary tree from preorder and inorder traversals
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  • Disjoint IntervalsImplement a function to determine the minimum amount of removals to get non-overlapping intervals
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  • End of Array ReachableImplement a function to determine if the end of the array is reachable
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  • Find the Longest Palindromic SubstringImplement a function to find the longest palindromic substring
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  • Find Word in GridImplement a function to check the existence of a word in a grid
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  • Graph Count Connected ComponentsImplement a function to count connected components in a graph
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  • Longest Common SubsequenceImplement a function to find the longest common subsequence in two strings
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  • Longest Non-repeating SubstringImplement a function to find the length of longest substring with unique characters
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  • Longest Repeating Substring After ReplacementsImplement a function to find the longest uniform substring after up to k replacements
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  • Matrix RotationImplement a function to rotate the given matrix by 90 degrees
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  • Matrix Spiral TraversalImplement a function to traverse the matrix in spiral order
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  • Merge New IntervalImplement a function to insert a new interval in the given intervals
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  • Neighborhood Theft (Circular)Implement a function to find maximum money to rob in circular houses without alerting police
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  • Ocean FlowImplement a function returning cells with water flow to both oceans
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  • Word FinderImplement a data structure where words can be added and support wildcard searching
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  • Graph CloneImplement a function to deeply clone a connected and undirected graph
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  • Minimum Meeting Rooms NeededImplement a function to find the minimum number of required conference rooms
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  • Binary Tree Serialization and DeserializationImplement a function to serialize and deserialize a binary tree
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  • Binary Tree Maximum Total PathImplement a function to find the maximum total of nodes in a binary tree path
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  • Find Words in GridImplement a function to find all the words present in the grid
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  • Linked Lists Combine K SortedImplement a function to combine k sorted linked lists
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  • Shortest Substring Containing CharactersImplement a function to return the smallest substring of a string containing all characters from another string
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  • Extraterrestrial LanguageImplement a function to verify and return an extraterrestrial language's alphabet order
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  • Number Stream MedianImplement a function to find the median of a dynamic stream of integers
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JavaScript Data Structures and Algorithms Interview Questions and Answers

Data structures and algorithms (DSA) interviews are an unavoidable part of software engineering roles, particularly for positions at big tech companies. As a front-end engineer, mastering DSA is crucial for writing efficient, optimized, and scalable code. However, many front-end developers find themselves prioritizing UI frameworks and JavaScript intricacies over algorithmic problem-solving, leading to less practice and confidence in DSA topics.

The lack of tailored DSA resources for front-end engineers further complicates preparation. Most DSA materials are written for general software engineering roles, focusing on backend-heavy languages like Python, Java, and C++. While these are excellent for algorithmic explanations, they often overlook the specific tools and contexts relevant to front-end engineers.

Bridging the Gap for Front-End Engineers

To address these challenges, we've developed a comprehensive resource of JavaScript and TypeScript-focused data structures and algorithms questions tailored specifically for front-end developers. Created by former senior engineers and ex-interviewers at top tech companies, our materials are designed to help front-end engineers build confidence in DSA while staying grounded in the tools they use daily.

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  2. High-quality content by experts: Each question is carefully crafted by experienced engineers who have conducted interviews for leading tech companies, guaranteeing the highest quality and alignment with real interview standards.
  3. Front end specific contexts: The problems and solutions incorporate scenarios and constraints that front-end developers are likely to encounter in the real-world, ensuring the skills are practical and directly applicable.

Comprehensive Coverage of DSA Topics

Our resource spans a wide range of topics, from fundamental data structures to advanced algorithms. These include:

Key Data Structures:

  • Arrays: Understand how to manipulate and traverse arrays efficiently, solving problems like subarray sums and sliding window patterns.
  • Linked Lists: Gain insights into traversing, inserting, and deleting nodes in singly and doubly linked lists.
  • Stacks and Queues: Learn their applications in problems like balancing parentheses, breadth-first search, and undo functionality.
  • Trees and Graphs: Master tree traversal techniques (inorder, preorder, postorder), shortest path algorithms (Dijkstra, BFS), and graph search techniques.
  • Hash Tables: Solve problems involving efficient lookups, duplicates detection, and frequency counts.

Core Algorithms:

  • Sorting algorithms: Implement QuickSort, MergeSort, and Bubble Sort while understanding their time and space complexities.
  • Searching algorithms: Explore binary search, linear search, and their applications in real-world scenarios.
  • Recursion and dynamic programming: Solve problems involving recursion trees, overlapping subproblems, and dynamic programming patterns like knapsack, Fibonacci, and subsequence detection.

Real-Time Practice and Feedback

To make your preparation seamless and efficient, our platform provides an in-browser coding workspace that enables you to practice coding directly without any setup. Key features include:

  1. Instant feedback: Write code, run it against comprehensive automated test cases, and receive immediate feedback on correctness and performance. This mimics real interview conditions and helps you iterate faster.
  2. Detailed explanations: Each question is accompanied by a step-by-step breakdown, multiple solution approaches, and best practices, ensuring you grasp the underlying concepts and patterns thoroughly.
  3. Practical focus: Questions are designed to reflect real-world problem-solving scenarios, ensuring your skills are directly transferable to on-the-job challenges.

Benefits of Using Our Resource

  • Master DSA with JavaScript and TypeScript: Learn to implement efficient algorithms and data structures in the languages most relevant to your front-end role.
  • Confidence in interviews: Build confidence by practicing with problems modeled after actual interview questions asked at leading tech companies.
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  • Improve practical front end skills: Tackle challenges that improve your ability to write performant code and design scalable solutions, both critical for front-end development.

Related lists

Check out other lists of questions below if you're looking for something more specific: