Question 1

What are props in React?

Accepted Answer

Inputs passed from parent to child; read-only from the child's perspective. Props enable composition and reuse. Changing props triggers re-render (subject to memo). Don't mutate props.

Question 2

Why shouldn't you mutate props?

Accepted Answer

Props are owned by the parent; mutation breaks purity and one-way data flow. Copy then update in local state, or lift state and pass a setter/callback.

Question 3

What are children as a prop pattern?

Accepted Answer

Using props.children or explicit slots to inject nested UI into a wrapper. Enables layout components. Render props / function-as-children pass data downward dynamically.

Question 4

How do default props work with function components?

Accepted Answer

Destructure defaults in parameters: ({ size = 'md' }) => ... defaultProps on functions is legacy. Prefer parameter defaults and TypeScript optional props.

Question 5

Prop drilling — problems and alternatives?

Accepted Answer

Passing props through many layers that don't use them; use composition, context, or state libraries. Context for sparse global concerns. Composition (children) often beats deep drilling.

Question 6

How do you type props well in TypeScript?

Accepted Answer

Define a Props type/interface; use React.PropsWithChildren; narrow event types. Avoid any. Prefer discriminated unions for variant components. Export props types for reuse.

Props React Interview Questions

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