What are key in React?

In React, keys are special string attributes you assign to elements in a list to help React identify which items have changed, been added, or removed.

Example:

{items.map(item => (
  <li key={item.id}>{item.name}</li>
))}

Why they matter:

• Improve rendering performance.
• Prevent bugs during UI updates.
• Required for elements in arrays/lists.

✅ Use stable, unique values like id as keys — avoid using indexes unless necessary.