What are React keys and why are they important?

React keys help React identify which items in a list are changed, added, or removed. Keys

provide a stable identity for each element, allowing React to optimize re-renders.

• Important: Keys should be unique for each sibling component.
• Why important: Without keys, React has to re-render all list items when the list

changes, which can be inefficient.

Example:

const items = ['apple', 'banana', 'cherry'];
return (

<ul>

{items.map((item, index) => (

<li key={index}>{item}</li>

))}

</ul>

);

• Tip: It’s better to use a unique identifier (e.g., id) as a key instead of using index if

the list can change order or content dynamically.