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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 1–26 of 26 results
- AmazonMediumFrontend EngineerBuild Accessible Data-Loading Popovers for Multiple Buttons
This problem tests the ability to build a robust, accessible UI component that manages asynchronous data fetching, state synchronization, and DOM-level focus management.
Software Engineering FundamentalsOnsiteFrontendReactAccessibility - AmazonMediumFrontend EngineerDesign a Debounced Product Search Box
Design and implement an accessible, resilient product search-as-you-type component featuring debounced requests, race-condition handling via request cancellation, client-side caching, and keyboard navigation.
Software Engineering FundamentalsOnsitefrontendjavascriptreact - AmazonMediumFrontend EngineerPredict JavaScript let and var Behavior
Tests deep understanding of JavaScript variable declarations (var vs let), focusing on hoisting, the Temporal Dead Zone (TDZ), block vs function scoping, and per-iteration lexical bindings in asynchronous loops.
Software Engineering FundamentalsOnsitejavascriptclosureshoisting - AndurilMediumFrontend EngineerDiagnose a Memory Leak in a JavaScript Web Application
Tests your ability to identify common JavaScript memory leak patterns—such as detached DOM trees, uncleared event subscriptions, and unbounded closures—and verify resolution using browser heap profiling techniques.
Software Engineering FundamentalsOnsiteJavaScriptPerformanceMemory Management - CohereMediumFrontend EngineerBuild a Credit Card Form With Validation and Linked Input Fields
A front-end UI coding question: build a credit card form with card number, name, expiry and security code, where every field is validated and the fields are linked, so the detected card network changes formatting and security-code rules. It tests state design, caret-safe input formatting, error timing, accessibility and safe handling of card data.
Software Engineering FundamentalsOnsite - CoinbaseHardFrontend EngineerImplement a Reusable Dropdown Component
This question evaluates skills in reusable frontend component design, including API design, state management (controlled vs uncontrolled), event handling, keyboard navigation, and accessibility (roles, focus behavior, and ARIA) for production-ready UI components.
Software Engineering FundamentalsOnsite - DatabricksMediumFrontend EngineerImplement Resilient Autocomplete Data Fetching
Implement resilient autocomplete fetching with a quiet period, bounded retries, newest-query precedence, and reuse of recent results. Cover empty input, out-of-order responses, cancellation during waits and requests, error classification, freshness and capacity policies, unmount safety, accessibility, shared requests, and responsive ranking.
Software Engineering FundamentalsOnsite - GleanMediumFrontend EngineerBuild a React Social Feed with Upvote/Downvote Re-Sorting and Pinned Posts
Build a React social feed where upvotes and downvotes re-sort posts by score in descending order and pinned posts stay at the top. Tests state design and immutable updates, correct vote-toggle arithmetic, deterministic ordering, accessibility and optimistic persistence with rollback.
Software Engineering FundamentalsOnsite - GleanMediumFrontend EngineerImplement Two-Player Connect Four on a 6x7 Board with Win and Draw Detection
Implement two-player Connect Four on a 6x7 board: drop discs into columns, detect four in a row in every direction, handle full columns and draws, and render a playable interface. Tests clean separation of game logic from UI, efficient win checks from the last move and careful edge handling.
Software Engineering FundamentalsOnsite - HubSpotMediumFrontend EngineerJavaScript Fundamentals: Prototype Chains and How 'this' Is Bound
A JavaScript fundamentals question that asks you to predict and explain how this is bound in method calls, detached calls, bound functions and arrow functions, trace property lookup through a prototype chain, and rewrite constructor-based inheritance with class syntax. It tests precise reasoning about core language behaviour.
Software Engineering FundamentalsOnsite - StripeMediumFrontend EngineerBuild and Optimize a React Interface Against an Undocumented API
Tests your ability to inspect an opaque or changing backend endpoint, build a resilient React component with typed normalization and client-side caching, and handle edge cases gracefully.
Software Engineering FundamentalsOnsitereacttypescriptcaching - 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 - 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 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 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 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
Amazon
Cohere
Coinbase
Databricks
Glean
HubSpot
Stripe
Tradedesk
UiPath
Verkada
Waymo
Zoox
xAI