React State Management

Question 1

What is lifting state up in React?

Accepted Answer

Moving shared state to the closest common ancestor component so multiple children can access it

Answer

When multiple components need the same data, the state is moved to their nearest common parent, which passes it down via props.

Question 2

What is the Context API?

Accepted Answer

A React feature for sharing data globally across components without passing props through every level

Answer

Context provides a way to share values (like themes, user data, preferences) across the component tree without explicit prop passing at every level.

Question 3

What is useReducer?

Accepted Answer

A hook for managing complex state logic with a reducer function, similar to Redux patterns

Answer

useReducer is an alternative to useState for complex state logic. It uses a reducer function that takes current state and an action, returning new state.

Question 4

What triggers a re-render in React?

Accepted Answer

State changes via setState/useState, parent re-renders passing new props, or context value changes

Answer

React re-renders when state changes, when a parent passes different props, or when consumed context values change. This triggers reconciliation with the virtual DOM.

Question 5

What is immutability in React state?

Accepted Answer

The practice of creating new objects/arrays instead of modifying existing ones when updating state

Answer

React relies on reference comparison to detect changes. Mutating state directly does not trigger re-renders. Creating new objects/arrays ensures React detects the change.

React Practice Test

React Practice Test

React State Management