React REACT 3

Question 1

What problem does React Context primarily solve?

Accepted Answer

Passing data deeply without prop drilling

Answer

Context lets you share values across the tree without manually passing props at every level.

Question 2

When does a component re-render by default?

Accepted Answer

When its state or props change

Answer

A component re-renders when its own state changes or it receives new props.

Question 3

What does React.memo do to a functional component?

Accepted Answer

Skips re-rendering if props are unchanged

Answer

React.memo performs a shallow prop comparison and skips re-rendering when props are equal.

Question 4

What is the second argument to useEffect?

Accepted Answer

A dependency array controlling when it runs

Answer

The dependency array tells React which values to watch to decide when the effect re-runs.

Question 5

What happens if you call a state setter with the same value as current state?

Accepted Answer

React may bail out and skip re-rendering

Answer

If the new state is identical (Object.is) to the current state, React can bail out of re-rendering.

React Practice Test