React Keys MCQ Keys Practice Questions

Direction: Choose the correct option

Why are keys important in React lists?

A. They are used for event handling

B. They help React identify which items changed for efficient updates

C. They improve accessibility

D. They are required for styling

Direction: Choose the correct option

What makes a good key?

A. Random number

B. Any string

C. Index

D. A unique and stable identifier from the data

Direction: Choose the correct option

What issue can using array index as key cause?

A. Syntax error

B. No issues

C. Poor performance

D. Component state may get mixed up when items are reordered

Direction: Choose the correct option

Can keys be duplicated across different lists?

A. Yes, duplication is fine

B. No, they cause errors

C. No, keys must be globally unique

D. Yes, keys only need to be unique within the same list

Direction: Choose the correct option

What does React do if two elements in a list have the same key?

A. Ignores the second

B. Renders both but shows a warning

C. Renders only the first

D. Throws an error

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