key prop

A special string attribute used on list items to help React identify which items changed, were added, or removed.

Syntax

react

<Component key={uniqueId} />

Example

react

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

// Avoid using array index as key when list can reorder:
// BAD:  key={index}
// GOOD: key={item.id}