Interview Questions
Context API provides a way to pass data through the component tree without having to pass props manually at every level. It solves prop drilling issues and enables global state management for specific data that needs to be accessed by many components.
The core components are: React.createContext() to create a context, Context.Provider to wrap components that need access to the context value, and Context.Consumer or useContext hook to consume the context value.
Create context using React.createContext(defaultValue) and provide it using the Provider component: <MyContext.Provider value={value}>{children}</MyContext.Provider>. The value prop can be any JavaScript value.
useContext is a hook that provides a cleaner way to consume context in functional components. Context.Consumer uses render props pattern and is mainly used in class components or when you need to consume multiple contexts in a single component.
Pass functions through context to update values, use state management with context, ensure proper value memoization. Consider performance implications of context updates and implement proper provider structure.
Context triggers re-renders in all consuming components when its value changes. Optimize by splitting contexts, using memoization, and considering component structure. Avoid putting frequently changing values in context.
Create separate contexts for different concerns, nest providers, and consume contexts independently. Consider context composition and proper separation of concerns.
Default value is used when a component consumes context but isn't wrapped in a provider. It's useful for testing, default states, and fallback values. Should represent valid context state.
Use React.memo on consuming components, memoize context value with useMemo, implement proper value comparison. Consider component structure and update patterns.
Context selectors help consume specific parts of context to prevent unnecessary re-renders. Implement using custom hooks, memoization, and proper state structure.
Use static contextType for single context or Context.Consumer for multiple contexts. Access context through this.context or render props pattern.
Use useReducer with Context for complex state management, implement proper action dispatching, handle state updates efficiently. Similar to Redux pattern but lighter weight.
Wrap components in test providers, mock context values, test context updates and consumer behavior. Consider using testing utilities and proper test setup.
Keep context values focused and minimal, separate state and updaters, consider memoization needs. Structure context based on usage patterns and update frequency.
Combine Context with useEffect for async operations, handle loading and error states, implement proper state updates. Consider async patterns and error boundaries.
Compose multiple contexts to separate concerns, improve maintainability, and optimize performance. Use when different parts of the app need different subsets of global state.
Initialize context with meaningful default values, consider lazy initialization, handle initial state properly. Implement proper type checking and documentation.
Overusing context, unnecessary re-renders, improper value memoization, context hell (too many nested providers). Consider alternatives and proper architecture.
Create theme context, provide theme values, implement theme switching, handle dynamic themes. Consider performance and SSR implications.
Use context for form state management, implement proper validation, handle field updates efficiently. Consider form complexity and performance requirements.
Define proper types for context values, use generic types when needed, implement type checking. Consider type safety and proper interface definitions.
Context complements props by providing a way to share values without explicit passing. Use context for truly global state, props for component-specific data.
Implement storage synchronization, handle hydration, manage persistence lifecycle. Consider storage options and state reconciliation.
Store auth state in context, handle auth flows, implement proper security measures. Consider token management and session handling.
Use error boundaries with context, handle error states, implement proper error propagation. Consider error recovery and user feedback.
Use clear naming conventions, organize contexts by feature/domain, implement proper file structure. Consider maintainability and scalability.
Implement proper cleanup in effects, handle unmount scenarios, manage resource disposal. Consider memory leaks and cleanup timing.
Create contexts dynamically, handle context creation lifecycle, manage dynamic providers. Consider performance and maintenance implications.
Document context purpose, value structure, update patterns, and usage examples. Consider documentation maintainability and clarity.