Component State Management Questions

Covers approaches and patterns for managing user interface state within component-based front end frameworks such as React and Angular. Topics include local component state, lifting state up, one way data flow, controlled versus uncontrolled components, prop passing and change handling, avoiding stale closures and missing dependency arrays, component composition patterns, performance considerations to prevent unnecessary re renders, and when to choose built in mechanisms versus external state libraries. For React this includes hooks such as useState, useContext, useReducer, useCallback, and useMemo and the trade offs of Context versus external stores. For Angular this includes using components and services, dependency injection, reactive programming patterns with observable streams, and change detection strategies. Candidates may be asked to compare state architectures, justify trade offs between simplicity and scalability, refactor components to improve state locality and performance, and design data flow for a feature from user interaction to persistent update.

MediumSystem Design

60 practiced

Design a state strategy for a notifications system in a medium-size web app. Requirements: real-time updates via WebSocket, persistent storage in backend, deduplication, and a toast UI with both transient toasts and persistent notification list. Describe how you would partition state between local component state, shared client state, and server sync.

EasyTechnical

75 practiced

As a Full-Stack Developer, explain the difference between local component state and global application state in component-based frameworks such as React and Angular. Provide practical short examples of when each is appropriate (e.g., input visibility vs. user session), and mention how UX and accessibility considerations influence that choice.

MediumTechnical

57 practiced

Create a custom React hook in TypeScript: useDebouncedState(initialValue, delay). The hook should behave like useState but delay updates to the returned debounced value by 'delay' milliseconds, cancel previous timers when the setter is called, and expose a flush() method to immediately apply pending updates. Provide the hook implementation and a short usage example.

HardTechnical

107 practiced

You're building a high-traffic dashboard with many widgets consuming shared data that updates frequently. Propose a client-side caching and invalidation strategy (use of normalized caches, subscriptions, or libraries like React Query) to minimize network calls and reduce re-renders while ensuring the UX shows fresh data when needed.

EasyTechnical

68 practiced

Explain controlled versus uncontrolled components in React, including trade-offs for form validation, UX, and performance. Also mention the Angular counterparts (template-driven vs reactive forms) and when you would choose each approach in a full-stack project.

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