Error Handling & Debugging Interview Questions

JavaScript provides several built-in error types for specific scenarios. TypeError indicates incorrect type operations, ReferenceError signals undefined variable access, SyntaxError represents parsing issues, RangeError indicates invalid numeric ranges, and Error serves as the base class. Custom errors should extend Error for specific application needs. When throwing errors, select the most appropriate type to facilitate debugging and error handling. Consider error message clarity and include relevant context for effective troubleshooting.

Asynchronous error handling requires careful consideration of Promise chains and async/await patterns. Use catch blocks strategically in Promise chains to handle specific error types. With async/await, implement try-catch blocks around await statements. Consider error propagation, implement proper cleanup in finally blocks, and handle uncaught rejections with window.onunhandledrejection. Ensure proper error logging and monitoring for production environments. Document error recovery strategies and implement appropriate fallback mechanisms.

Modern browsers offer comprehensive debugging tools including breakpoints, step debugging, watch expressions, and call stack analysis. Chrome DevTools and Firefox Developer Tools provide source maps support, network request monitoring, and performance profiling. Utilize console methods beyond console.log, such as console.trace for stack traces, console.table for structured data, and console.group for organized logging. Implement proper source map generation in build process for accurate debugging of minified code.

Custom error types should extend the built-in Error class and include additional context relevant to the application domain. Implement proper stack trace capture, maintain error hierarchies for specific error categories, and include helpful error messages. Consider serialization needs for error reporting, implement proper instanceof behavior, and document error type usage patterns. Ensure custom errors integrate well with existing error handling mechanisms.

Production error logging requires careful consideration of security, performance, and debugging needs. Implement structured logging formats, include relevant context without sensitive data, and ensure proper error aggregation. Use logging services with appropriate security measures, implement rate limiting for error reporting, and maintain error categorization. Consider log rotation, implement proper cleanup, and document logging requirements.

Memory leak detection requires systematic approach using Chrome DevTools Memory panel or similar tools. Profile memory usage, analyze heap snapshots, and identify retained objects. Common causes include undisposed event listeners, closure references, and detached DOM elements. Implement proper cleanup mechanisms, monitor memory usage patterns, and document memory management requirements. Regular profiling helps identify potential issues early.

Production debugging requires comprehensive error logging, source map support, and monitoring tools. Implement detailed error tracking, maintain proper logging levels, and ensure stack traces are preserved. Use feature flags for gradual rollouts, implement proper versioning, and maintain debugging endpoints. Consider performance impact of debugging features and implement appropriate security measures.

Error boundaries provide containment for runtime errors, preventing application-wide crashes. Implement hierarchical error handling, provide fallback UI components, and maintain proper error reporting. Consider component isolation, implement recovery mechanisms, and document error boundary behavior. Handle async errors appropriately and maintain proper cleanup procedures.

Third-party script errors require careful isolation and error handling strategies. Implement proper script loading error handling, use try-catch blocks around third-party code execution, and maintain error boundaries. Consider script timeout handling, implement fallback mechanisms, and document integration requirements. Monitor third-party script performance and errors separately.

Error recovery requires systematic approach to restore application state and functionality. Implement proper state backup mechanisms, handle partial failures appropriately, and provide user feedback. Consider recovery priorities, implement proper retry mechanisms, and document recovery procedures. Maintain proper cleanup during recovery process.

Performance debugging utilizes browser performance tools, profiling, and timeline analysis. Use Performance panel for runtime analysis, identify bottlenecks through flame charts, and analyze rendering performance. Consider network optimization, implement proper performance monitoring, and document performance requirements. Regular profiling helps maintain optimal performance.

API error handling requires comprehensive strategy for different error types and scenarios. Handle network errors, timeout conditions, and invalid responses appropriately. Implement retry mechanisms, maintain proper error status mapping, and provide user feedback. Consider error response formats, implement proper validation, and document API error handling requirements.

Event-driven code debugging requires understanding of event flow and timing. Use debugger statements strategically, implement proper event logging, and analyze event sequences. Consider async event handling, implement proper event cleanup, and document event debugging approaches. Maintain proper event monitoring in production.

Worker thread error handling requires proper message passing and error propagation. Implement error event listeners, handle termination conditions, and maintain proper cleanup. Consider worker lifecycle management, implement proper error reporting, and document worker error handling requirements. Handle resource cleanup appropriately.

Error messages should be clear, actionable, and provide appropriate context. Include error codes, relevant details, and recovery steps when applicable. Consider internationalization requirements, implement proper message formatting, and maintain consistent error message structure. Document error message standards and maintain proper validation.

Micro-frontend error tracking requires coordinated error handling strategy. Implement proper error propagation between components, maintain consistent error reporting, and handle cross-application errors. Consider error boundary implementation, maintain proper error isolation, and document integration requirements.

Race condition debugging requires systematic analysis of timing and state changes. Implement proper logging of state transitions, use async debugging tools, and analyze execution order. Consider concurrent operation handling, implement proper synchronization, and document race condition patterns.

Component lifecycle error handling requires proper error boundaries and cleanup procedures. Implement error handling for initialization, update, and cleanup phases. Consider state consistency, implement proper error recovery, and document lifecycle error patterns. Maintain proper error isolation between components.

Minified code debugging requires proper source map integration and build process configuration. Maintain source map generation, implement proper error stack translation, and ensure proper file organization. Consider source map security, implement proper deployment procedures, and document debugging setup requirements.

Environment-specific error reporting requires appropriate configuration and handling. Implement proper error filtering, maintain environment-specific logging levels, and handle sensitive data appropriately. Consider compliance requirements, implement proper security measures, and document environment-specific procedures.

Memory consumption debugging requires systematic analysis using browser memory tools. Profile heap usage, analyze allocation patterns, and identify memory leaks. Consider garbage collection impact, implement proper memory monitoring, and document memory optimization strategies. Regular profiling helps maintain optimal memory usage.

Service worker error handling requires proper event handling and recovery mechanisms. Implement error listeners, handle installation and activation errors, and maintain proper cleanup. Consider offline operation handling, implement proper caching strategies, and document service worker error patterns.

Recursive function debugging requires careful analysis of call stack and state changes. Implement proper logging at each recursion level, use conditional breakpoints, and analyze termination conditions. Consider stack overflow prevention, implement proper error handling, and document recursive patterns.

Client-side routing error monitoring requires proper route change handling and error tracking. Implement route transition error handling, maintain proper history state, and handle navigation errors. Consider deep linking issues, implement proper error recovery, and document routing error patterns.

Validation error handling requires comprehensive strategy for different validation scenarios. Implement proper error collection, maintain error state, and provide appropriate user feedback. Consider form validation timing, implement proper error display, and document validation requirements.

WebSocket error tracking requires proper connection state monitoring and error handling. Implement connection error handling, manage reconnection attempts, and maintain proper cleanup. Consider network conditions, implement proper timeout handling, and document connection error patterns.

Application state debugging requires proper state monitoring and analysis tools. Use Redux DevTools or similar state inspection tools, implement state logging, and analyze state transitions. Consider complex state interactions, implement proper state validation, and document state debugging procedures.

Browser extension error handling requires proper isolation and error reporting. Implement content script error handling, manage background script errors, and maintain proper communication error handling. Consider cross-origin restrictions, implement proper security measures, and document extension-specific requirements.

Mobile browser error handling requires consideration of device-specific issues and limitations. Handle touch event errors, manage memory constraints, and implement proper offline error handling. Consider mobile network conditions, implement proper performance monitoring, and document mobile-specific requirements.