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Frontend Engineer Interview Questions
Practice 9403 coding, system design and machine learning questions from 546 companies, sorted by role, topic and interview round. Every question has step-by-step hints, a code runner that supports 8 languages and an AI mentor; members also get the full solution walkthrough.
- 9403
- Questions
- 546
- Companies
- 11
- Topics
- 8
- Languages
Showing 31–53 of 53 results
- TradedeskMediumFrontend EngineerDebug a Frontend Component That Shows Wrong API Results
A front-end debugging question in which a React component that fetches data sometimes shows results that do not match the current input, even though each API response is correct. It tests how the candidate reproduces a timing-dependent bug, finds the root cause, fixes it in the effect, handles cancellation errors, and verifies the fix with a deterministic test.
Software Engineering FundamentalsOnsite - TradedeskMediumFrontend EngineerImplement a Publish-Subscribe Event Bus in JavaScript or TypeScript
A front-end coding question asking the candidate to implement an in-process publish-subscribe utility in JavaScript or TypeScript with subscribe, publish, and unsubscribe. It tests API design, choice of data structures, safe iteration when subscribers change during a publish, isolation of subscriber errors, and cleanup that avoids memory leaks.
Software Engineering FundamentalsOnsite - TradedeskMediumFrontend EngineerObject-Oriented Design of an Elevator Control System
An object-oriented design question asking the candidate to model an elevator control system: its classes, their responsibilities, and how a button press becomes an elevator stop. It tests requirement scoping, a clear per-car state model, stop ordering and dispatch policies that can be swapped out, handling of out-of-service cars and duplicate requests, and testability.
Software Engineering FundamentalsOnsite - UiPathEasyFrontend EngineerBuild an Event-Driven Folder Browser
This problem tests your ability to model hierarchical data structures and design an efficient state management strategy for an interactive UI component.
Software Engineering FundamentalsOnsiteData StructuresFrontend ArchitectureState Management - VerkadaMediumFrontend EngineerBuild a React dashboard with filters
This problem tests your ability to build a modular React dashboard that handles state synchronization, efficient list filtering, and semantic UI structure.
Software Engineering FundamentalsOnsiteReactFrontendState Management - VerkadaMediumFrontend EngineerImplement a recency cache and min-coins DP
This problem tests your ability to combine a Least Recently Used (LRU) cache mechanism with a dynamic programming approach for optimization.
Coding & AlgorithmsOnsiteHash MapDoubly Linked ListDynamic Programming - WaymoMediumFrontend EngineerBuild a Debounced Autocomplete Search Bar
This problem evaluates your ability to implement a robust, performant search component that handles asynchronous race conditions and user accessibility requirements.
Software Engineering FundamentalsOnsiteJavaScriptFrontendDOM - WaymoMediumFrontend EngineerBuild an Autocomplete Search Bar With a Hand-Written Debounce
Build an autocomplete search bar that fetches suggestions as the user types, with a hand-written debounce. Tests timer handling across renders, out-of-order responses and request cancellation, keyboard navigation, accessibility, cleanup and testing with fake timers.
Software Engineering FundamentalsOnsite - WaymoMediumFrontend EngineerDebug an Angular UI from User Reports
This problem tests your ability to debug an Angular component, specifically focusing on Change Detection strategies, memory leaks in RxJS subscriptions, and asynchronous state management.
Software Engineering FundamentalsOnsiteAngularRxJSMemory Management - WaymoMediumFrontend EngineerDesign the Frontend for an AI Chat Application
This question tests the ability to design a performant and resilient frontend architecture for a real-time, state-heavy AI chat interface capable of handling large message trees and network instability.
System DesignOnsiteFrontendState ManagementWebSockets - WaymoMediumFrontend EngineerDesign the Frontend of an AI Chat Application With Streaming Replies
Frontend-focused system design for an AI chat application. It covers component structure, conversation and message state, streaming replies, stop and retry, safe rendering of model output, performance on long conversations, accessibility and the backend API contract.
System DesignOnsite - WaymoMediumFrontend EngineerFilter Matching Subtrees from an N-Ary Tree
This problem tests tree traversal techniques, string matching, and the ability to handle iterative tree processing to avoid stack overflow in deep structures.
Coding & AlgorithmsOnsiteTreesN-ary TreeAlgorithms - WaymoMediumFrontend EngineerFilter an N-ary Tree by Substring and Render It With Indentation in a UI
Filter an n-ary tree by removing every node whose value contains a substring, along with its subtree, then build a UI that renders the filtered tree with depth-based indentation as the user types. Tests recursion, immutability, state design and rendering.
Software Engineering FundamentalsOnsite - WaymoMediumFrontend EngineerRun Promise Tasks with Bounded Concurrency
Implement an asynchronous task runner in TypeScript that limits concurrent execution, handles synchronous throws and rejections gracefully, and returns settled results in the original task order.
Software Engineering FundamentalsOnsiteTypeScriptConcurrencyPromises - ZooxHardFrontend EngineerBuild a Stateful Calculator
This question tests the ability to manage complex state transitions in a UI component, specifically handling input sequences, operator precedence, and state consistency in a stateful calculator.
Software Engineering FundamentalsOnsiteFrontendState ManagementFSM - xAIMediumFrontend EngineerBuild a React Typeahead with Async Suggestions and Keyboard Navigation
A frontend coding question: build a React typeahead, a search input whose dropdown shows suggestions fetched asynchronously as the user types. The dropdown must support arrow keys, Enter, Escape and mouse selection, so it tests hooks, handling of out-of-order responses, accessibility and UI state.
Software Engineering FundamentalsOnsite - xAIMediumFrontend EngineerDesign a Collaborative Document Editor
Design collaborative editing with an explicit operation model, OT or CRDT convergence, durable history, reconnect recovery, access control, and separate presence state.
System DesignOnsite - xAIMediumFrontend EngineerDesign a Real-Time Collaborative Document Editor with Concurrent Edits
A system design question for a frontend engineer: design a collaborative document editor where several people edit the same document at once and see each other's changes in near real time. It tests conflict resolution for concurrent edits, client-side state, the sync protocol, persistence and presence.
System DesignOnsite - xAIMediumFrontend EngineerImplement an Asynchronous React Typeahead
Implement a debounced React typeahead with stale-response protection, cancellation, loading/error states, keyboard selection, and accessible combobox semantics.
Software Engineering FundamentalsOnsite - xAIMediumFrontend EngineerLoad and Display a React List with useEffect
Load a React list with useEffect while handling endpoint changes, cleanup, stale responses, HTTP and schema errors, stable keys, and user-visible states.
Software Engineering FundamentalsOnsite - xAIMediumFrontend EngineerPlan a Project Across Customers and Partner Teams
Plan a cross-team customer project through outcome clarification, dependency ownership, milestone evidence, uncertainty, scope tradeoffs, and clear stakeholder communication.
Product / Decision MakingOnsite - xAIMediumFrontend EngineerRender Nested JSON in a Code-Style Viewer
Render nested JSON safely in React with indentation, type styling, collapsible containers, empty values, and explicit boundaries between a viewer and an editor.
Software Engineering FundamentalsOnsite - xAIMediumFrontend EngineerWalk Through a Past Frontend Project: Problems Solved and Tech Stack Choices
A behavioral question from a project and product management round for a frontend role: describe a problem you hit on a past project and how you solved it, then explain how you chose the tech stack. It tests structured storytelling, trade-off reasoning, and decisions tied to product needs.
Behavioral & LeadershipOnsite
Tradedesk
UiPath
Verkada
Waymo
Zoox
xAI